feat(11-02): add DAO queries, update CalendarDayState, implement pre-population provider

- Add watchAllActiveRecurringTasks() and watchAllActiveRecurringTasksInRoom() to CalendarDao
- Add watchCompletionsInRange() for period-completion filtering
- Extend CalendarDayState with prePopulatedTasks field (default empty, backward compat)
- Update isEmpty getter to include prePopulatedTasks.isEmpty
- Add _isInCurrentIntervalWindow() and _calculatePreviousDueDate() helpers
- Rewrite calendarDayProvider and roomCalendarDayProvider with pre-population logic
- Fix _subtractMonths() year-boundary bug using total-month arithmetic
- Add 9 new DAO tests for watchAllActiveRecurringTasks, watchAllActiveRecurringTasksInRoom, watchCompletionsInRange

lib/features/home/data/calendar_dao.dart

@@ -165,4 +165,59 @@ class CalendarDao extends DatabaseAccessor<AppDatabase>
     final result = await query.getSingle();
     return result.read(countExp) ?? 0;
   }
+
+  /// Watch ALL active tasks with their rooms.
+  ///
+  /// Used by the pre-population logic to determine which tasks should appear
+  /// on days within their current interval window (before their next due date).
+  Stream<List<TaskWithRoom>> watchAllActiveRecurringTasks() {
+    final query = select(tasks).join([
+      innerJoin(rooms, rooms.id.equalsExp(tasks.roomId)),
+    ]);
+    query.where(tasks.isActive.equals(true));
+    query.orderBy([OrderingTerm.asc(tasks.name)]);
+
+    return query.watch().map((rows) {
+      return rows.map((row) {
+        final task = row.readTable(tasks);
+        final room = row.readTable(rooms);
+        return TaskWithRoom(task: task, roomName: room.name, roomId: room.id);
+      }).toList();
+    });
+  }
+
+  /// Watch ALL active tasks with their rooms, filtered to a specific [roomId].
+  ///
+  /// Room-scoped variant of [watchAllActiveRecurringTasks], used by
+  /// [roomCalendarDayProvider] to pre-populate tasks for a single room.
+  Stream<List<TaskWithRoom>> watchAllActiveRecurringTasksInRoom(int roomId) {
+    final query = select(tasks).join([
+      innerJoin(rooms, rooms.id.equalsExp(tasks.roomId)),
+    ]);
+    query.where(tasks.isActive.equals(true) & tasks.roomId.equals(roomId));
+    query.orderBy([OrderingTerm.asc(tasks.name)]);
+
+    return query.watch().map((rows) {
+      return rows.map((row) {
+        final task = row.readTable(tasks);
+        final room = row.readTable(rooms);
+        return TaskWithRoom(task: task, roomName: room.name, roomId: room.id);
+      }).toList();
+    });
+  }
+
+  /// Watch completions for a given [taskId] within a date range [start]..[end].
+  ///
+  /// Used for period-completion filtering: if a task was completed in the
+  /// current interval window, it should not appear as a pre-populated task.
+  /// [start] is inclusive; [end] is exclusive.
+  Stream<List<TaskCompletion>> watchCompletionsInRange(
+      int taskId, DateTime start, DateTime end) {
+    return (select(taskCompletions)
+          ..where((c) =>
+              c.taskId.equals(taskId) &
+              c.completedAt.isBiggerOrEqualValue(start) &
+              c.completedAt.isSmallerThanValue(end)))
+        .watch();
+  }
 }

lib/features/home/domain/calendar_models.dart

@@ -1,11 +1,17 @@
 import 'package:household_keeper/features/home/domain/daily_plan_models.dart';
 
-/// State for the calendar day view: tasks for the selected date + overdue tasks.
+/// State for the calendar day view: tasks for the selected date + overdue tasks
+/// + pre-populated tasks within the current interval window.
 class CalendarDayState {
   final DateTime selectedDate;
   final List<TaskWithRoom> dayTasks;
   final List<TaskWithRoom> overdueTasks;
 
+  /// Tasks visible via pre-population: recurring tasks whose nextDueDate is in
+  /// the future but whose current interval window includes [selectedDate].
+  /// These are shown with muted styling to distinguish them from due-today tasks.
+  final List<TaskWithRoom> prePopulatedTasks;
+
   /// Total number of tasks in the database (across all days/rooms).
   /// Used by the UI to distinguish first-run empty state (no tasks exist at all)
   /// from celebration state (tasks exist but today's are all done).
@@ -15,11 +21,11 @@ class CalendarDayState {
     required this.selectedDate,
     required this.dayTasks,
     required this.overdueTasks,
+    this.prePopulatedTasks = const [],
     required this.totalTaskCount,
   });
 
-  /// True when both day tasks and overdue tasks are empty.
-  /// Determined by the UI layer (completion state vs. no tasks at all
-  /// is handled in the widget based on this flag and history context).
-  bool get isEmpty => dayTasks.isEmpty && overdueTasks.isEmpty;
+  /// True when day tasks, overdue tasks, and pre-populated tasks are all empty.
+  bool get isEmpty =>
+      dayTasks.isEmpty && overdueTasks.isEmpty && prePopulatedTasks.isEmpty;
 }

lib/features/home/presentation/calendar_providers.dart

@@ -3,9 +3,12 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:household_keeper/core/providers/database_provider.dart';
 import 'package:household_keeper/features/home/domain/calendar_models.dart';
 import 'package:household_keeper/features/home/domain/daily_plan_models.dart';
+import 'package:household_keeper/features/tasks/domain/frequency.dart';
 import 'package:household_keeper/features/tasks/domain/task_sort_option.dart';
 import 'package:household_keeper/features/tasks/presentation/sort_preference_notifier.dart';
 
+import '../../../core/database/database.dart';
+
 /// Notifier that manages the currently selected date in the calendar strip.
 ///
 /// Defaults to today (start of day, time zeroed out).
@@ -60,13 +63,82 @@ List<TaskWithRoom> _sortTasks(
   return sorted;
 }
 
-/// Reactive calendar day state: tasks for the selected date + overdue tasks.
+/// Determines whether [task] should appear on [selectedDate] via pre-population.
+///
+/// Per D-07: A task shows on all days within the current interval window
+/// leading up to its nextDueDate. For example:
+/// - weekly task due Monday: shows on all 7 days (Tue-Mon) before nextDueDate
+/// - monthly task due 15th: shows on all ~30 days leading up to the 15th
+/// - daily task: shows every day (interval window = 1 day, always due today)
+bool _isInCurrentIntervalWindow(Task task, DateTime selectedDate) {
+  final dueDate = DateTime(
+      task.nextDueDate.year, task.nextDueDate.month, task.nextDueDate.day);
+  final selected =
+      DateTime(selectedDate.year, selectedDate.month, selectedDate.day);
+
+  // If selected date IS the due date, it is a "due today" task (not pre-populated)
+  if (selected == dueDate) return false;
+  // If selected date is after the due date, task is overdue (handled separately)
+  if (selected.isAfter(dueDate)) return false;
+
+  // Calculate the start of the current interval window:
+  // The previous due date = current nextDueDate minus one interval
+  final previousDue = _calculatePreviousDueDate(task);
+  final prevDay = DateTime(
+      previousDue.year, previousDue.month, previousDue.day);
+
+  // Selected date must be AFTER the previous due date (exclusive)
+  // and BEFORE the next due date (exclusive — due date itself is "dayTasks" not pre-pop)
+  return selected.isAfter(prevDay) && selected.isBefore(dueDate);
+}
+
+/// Reverse-calculate the previous due date by subtracting one interval.
+/// This gives the start of the current interval window.
+DateTime _calculatePreviousDueDate(Task task) {
+  switch (task.intervalType) {
+    case IntervalType.daily:
+      return task.nextDueDate.subtract(const Duration(days: 1));
+    case IntervalType.everyNDays:
+      return task.nextDueDate.subtract(Duration(days: task.intervalDays));
+    case IntervalType.weekly:
+      return task.nextDueDate.subtract(const Duration(days: 7));
+    case IntervalType.biweekly:
+      return task.nextDueDate.subtract(const Duration(days: 14));
+    case IntervalType.monthly:
+      return _subtractMonths(task.nextDueDate, 1, task.anchorDay);
+    case IntervalType.everyNMonths:
+      return _subtractMonths(task.nextDueDate, task.intervalDays, task.anchorDay);
+    case IntervalType.quarterly:
+      return _subtractMonths(task.nextDueDate, 3, task.anchorDay);
+    case IntervalType.yearly:
+      return _subtractMonths(task.nextDueDate, 12, task.anchorDay);
+  }
+}
+
+/// Subtract [months] from [date], respecting [anchorDay] clamping.
+///
+/// Uses total-month arithmetic to handle year-boundary crossings correctly
+/// (e.g. January - 1 month = December of the previous year).
+DateTime _subtractMonths(DateTime date, int months, int? anchorDay) {
+  // Convert date to total months from year 0 (0-indexed month), subtract, convert back.
+  final totalMonths = date.year * 12 + (date.month - 1) - months;
+  final targetYear = totalMonths ~/ 12;
+  final normalizedMonth = (totalMonths % 12) + 1;
+  final day = anchorDay ?? date.day;
+  final lastDay = DateTime(targetYear, normalizedMonth + 1, 0).day;
+  final clampedDay = day > lastDay ? lastDay : day;
+  return DateTime(targetYear, normalizedMonth, clampedDay);
+}
+
+/// Reactive calendar day state: tasks for the selected date + overdue tasks
+/// + pre-populated virtual instances within the current interval window.
 ///
 /// Overdue tasks are only included when the selected date is today.
 /// Past and future dates show only tasks originally due on that day.
 ///
 /// dayTasks are sorted in-memory according to the active [sortPreferenceProvider].
 /// overdueTasks retain their existing order (pinned at top, unsorted per design).
+/// prePopulatedTasks show tasks visible via interval-window pre-population.
 ///
 /// Defined manually (not @riverpod) because riverpod_generator has trouble
 /// with drift's generated [Task] type. Same pattern as [dailyPlanProvider].
@@ -81,6 +153,7 @@ final calendarDayProvider =
   final isToday = selectedDate == today;
 
   final dayTasksStream = db.calendarDao.watchTasksForDate(selectedDate);
+  final allTasksStream = db.calendarDao.watchAllActiveRecurringTasks();
 
   return dayTasksStream.asyncMap((dayTasks) async {
     final List<TaskWithRoom> overdueTasks;
@@ -94,12 +167,47 @@ final calendarDayProvider =
       overdueTasks = const [];
     }
 
+    // Get all active tasks for pre-population filtering
+    final allTasks = await allTasksStream.first;
+
+    // IDs of tasks already showing as due-today or overdue
+    final dueTodayIds = dayTasks.map((t) => t.task.id).toSet();
+    final overdueIds = overdueTasks.map((t) => t.task.id).toSet();
+
+    // Filter for pre-populated tasks
+    final prePopulated = <TaskWithRoom>[];
+    for (final tw in allTasks) {
+      // Skip if already showing as due-today or overdue
+      if (dueTodayIds.contains(tw.task.id)) continue;
+      if (overdueIds.contains(tw.task.id)) continue;
+
+      // Check if in current interval window
+      if (!_isInCurrentIntervalWindow(tw.task, selectedDate)) continue;
+
+      // Check if already completed in current period (D-09, D-10)
+      final prevDue = _calculatePreviousDueDate(tw.task);
+      final completions = await db.calendarDao
+          .watchCompletionsInRange(
+            tw.task.id,
+            DateTime(prevDue.year, prevDue.month, prevDue.day),
+            DateTime(tw.task.nextDueDate.year, tw.task.nextDueDate.month,
+                    tw.task.nextDueDate.day)
+                .add(const Duration(days: 1)),
+          )
+          .first;
+
+      if (completions.isEmpty) {
+        prePopulated.add(tw);
+      }
+    }
+
     final totalTaskCount = await db.calendarDao.getTaskCount();
 
     return CalendarDayState(
       selectedDate: selectedDate,
       dayTasks: _sortTasks(dayTasks, sortOption),
       overdueTasks: overdueTasks,
+      prePopulatedTasks: _sortTasks(prePopulated, sortOption),
       totalTaskCount: totalTaskCount,
     );
   });
@@ -122,6 +230,8 @@ final roomCalendarDayProvider =
 
   final dayTasksStream =
       db.calendarDao.watchTasksForDateInRoom(selectedDate, roomId);
+  final allTasksStream =
+      db.calendarDao.watchAllActiveRecurringTasksInRoom(roomId);
 
   return dayTasksStream.asyncMap((dayTasks) async {
     final List<TaskWithRoom> overdueTasks;
@@ -134,12 +244,47 @@ final roomCalendarDayProvider =
       overdueTasks = const [];
     }
 
+    // Get all active tasks in room for pre-population filtering
+    final allTasks = await allTasksStream.first;
+
+    // IDs of tasks already showing as due-today or overdue
+    final dueTodayIds = dayTasks.map((t) => t.task.id).toSet();
+    final overdueIds = overdueTasks.map((t) => t.task.id).toSet();
+
+    // Filter for pre-populated tasks
+    final prePopulated = <TaskWithRoom>[];
+    for (final tw in allTasks) {
+      // Skip if already showing as due-today or overdue
+      if (dueTodayIds.contains(tw.task.id)) continue;
+      if (overdueIds.contains(tw.task.id)) continue;
+
+      // Check if in current interval window
+      if (!_isInCurrentIntervalWindow(tw.task, selectedDate)) continue;
+
+      // Check if already completed in current period (D-09, D-10)
+      final prevDue = _calculatePreviousDueDate(tw.task);
+      final completions = await db.calendarDao
+          .watchCompletionsInRange(
+            tw.task.id,
+            DateTime(prevDue.year, prevDue.month, prevDue.day),
+            DateTime(tw.task.nextDueDate.year, tw.task.nextDueDate.month,
+                    tw.task.nextDueDate.day)
+                .add(const Duration(days: 1)),
+          )
+          .first;
+
+      if (completions.isEmpty) {
+        prePopulated.add(tw);
+      }
+    }
+
     final totalTaskCount = await db.calendarDao.getTaskCountInRoom(roomId);
 
     return CalendarDayState(
       selectedDate: selectedDate,
       dayTasks: _sortTasks(dayTasks, sortOption),
       overdueTasks: overdueTasks,
+      prePopulatedTasks: _sortTasks(prePopulated, sortOption),
       totalTaskCount: totalTaskCount,
     );
   });

test/features/home/data/calendar_dao_test.dart

@@ -1,3 +1,4 @@
+import 'package:drift/drift.dart' show Value;
 import 'package:drift/native.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:household_keeper/core/database/database.dart';
@@ -484,6 +485,225 @@ void main() {
     });
   });
 
+  group('CalendarDao.watchAllActiveRecurringTasks', () {
+    test('returns all active tasks', () async {
+      // Insert 2 active tasks and 1 inactive task
+      await db.tasksDao.insertTask(TasksCompanion.insert(
+        roomId: room1Id,
+        name: 'Aktive Aufgabe 1',
+        intervalType: IntervalType.weekly,
+        effortLevel: EffortLevel.low,
+        nextDueDate: DateTime(2026, 3, 20),
+      ));
+      await db.tasksDao.insertTask(TasksCompanion.insert(
+        roomId: room2Id,
+        name: 'Aktive Aufgabe 2',
+        intervalType: IntervalType.monthly,
+        effortLevel: EffortLevel.medium,
+        nextDueDate: DateTime(2026, 3, 25),
+      ));
+      // Insert inactive task (isActive defaults to true; manually set false via update)
+      final inactiveId = await db.tasksDao.insertTask(TasksCompanion.insert(
+        roomId: room1Id,
+        name: 'Inaktive Aufgabe',
+        intervalType: IntervalType.daily,
+        effortLevel: EffortLevel.low,
+        nextDueDate: DateTime(2026, 3, 16),
+      ));
+      await (db.update(db.tasks)..where((t) => t.id.equals(inactiveId)))
+          .write(const TasksCompanion(isActive: Value(false)));
+
+      final result =
+          await db.calendarDao.watchAllActiveRecurringTasks().first;
+      expect(result.length, 2);
+      final names = result.map((t) => t.task.name).toList();
+      expect(names, contains('Aktive Aufgabe 1'));
+      expect(names, contains('Aktive Aufgabe 2'));
+      expect(names, isNot(contains('Inaktive Aufgabe')));
+    });
+
+    test('returns tasks sorted alphabetically by name', () async {
+      await db.tasksDao.insertTask(TasksCompanion.insert(
+        roomId: room1Id,
+        name: 'Zuletzt',
+        intervalType: IntervalType.weekly,
+        effortLevel: EffortLevel.low,
+        nextDueDate: DateTime(2026, 3, 20),
+      ));
+      await db.tasksDao.insertTask(TasksCompanion.insert(
+        roomId: room2Id,
+        name: 'Als erstes',
+        intervalType: IntervalType.monthly,
+        effortLevel: EffortLevel.medium,
+        nextDueDate: DateTime(2026, 3, 25),
+      ));
+
+      final result =
+          await db.calendarDao.watchAllActiveRecurringTasks().first;
+      expect(result.length, 2);
+      expect(result[0].task.name, 'Als erstes');
+      expect(result[1].task.name, 'Zuletzt');
+    });
+
+    test('returns empty list when no active tasks exist', () async {
+      final result =
+          await db.calendarDao.watchAllActiveRecurringTasks().first;
+      expect(result, isEmpty);
+    });
+  });
+
+  group('CalendarDao.watchAllActiveRecurringTasksInRoom', () {
+    test('filters tasks by room', () async {
+      // Tasks in room1
+      await db.tasksDao.insertTask(TasksCompanion.insert(
+        roomId: room1Id,
+        name: 'Kueche Aufgabe',
+        intervalType: IntervalType.weekly,
+        effortLevel: EffortLevel.low,
+        nextDueDate: DateTime(2026, 3, 20),
+      ));
+      // Task in room2 (should NOT appear for room1)
+      await db.tasksDao.insertTask(TasksCompanion.insert(
+        roomId: room2Id,
+        name: 'Bad Aufgabe',
+        intervalType: IntervalType.monthly,
+        effortLevel: EffortLevel.medium,
+        nextDueDate: DateTime(2026, 3, 25),
+      ));
+
+      final result =
+          await db.calendarDao.watchAllActiveRecurringTasksInRoom(room1Id).first;
+      expect(result.length, 1);
+      expect(result.first.task.name, 'Kueche Aufgabe');
+      expect(result.first.roomId, room1Id);
+    });
+
+    test('returns empty list when room has no active tasks', () async {
+      final result =
+          await db.calendarDao.watchAllActiveRecurringTasksInRoom(room1Id).first;
+      expect(result, isEmpty);
+    });
+  });
+
+  group('CalendarDao.watchCompletionsInRange', () {
+    test('returns completions within date range', () async {
+      final taskId = await db.tasksDao.insertTask(TasksCompanion.insert(
+        roomId: room1Id,
+        name: 'Woechentliche Aufgabe',
+        intervalType: IntervalType.weekly,
+        effortLevel: EffortLevel.low,
+        nextDueDate: DateTime(2026, 3, 23),
+      ));
+
+      // Completion within range (March 18)
+      await db.into(db.taskCompletions).insert(TaskCompletionsCompanion.insert(
+        taskId: taskId,
+        completedAt: DateTime(2026, 3, 18, 10),
+      ));
+      // Completion within range (March 20)
+      await db.into(db.taskCompletions).insert(TaskCompletionsCompanion.insert(
+        taskId: taskId,
+        completedAt: DateTime(2026, 3, 20, 14),
+      ));
+      // Completion OUTSIDE range (before start — March 15)
+      await db.into(db.taskCompletions).insert(TaskCompletionsCompanion.insert(
+        taskId: taskId,
+        completedAt: DateTime(2026, 3, 15),
+      ));
+      // Completion OUTSIDE range (after end — March 25)
+      await db.into(db.taskCompletions).insert(TaskCompletionsCompanion.insert(
+        taskId: taskId,
+        completedAt: DateTime(2026, 3, 25),
+      ));
+
+      // Range: March 16 (inclusive) to March 24 (exclusive)
+      final result = await db.calendarDao
+          .watchCompletionsInRange(
+            taskId,
+            DateTime(2026, 3, 16),
+            DateTime(2026, 3, 24),
+          )
+          .first;
+      expect(result.length, 2);
+    });
+
+    test('returns empty list when no completions in range', () async {
+      final taskId = await db.tasksDao.insertTask(TasksCompanion.insert(
+        roomId: room1Id,
+        name: 'Keine Completions',
+        intervalType: IntervalType.weekly,
+        effortLevel: EffortLevel.low,
+        nextDueDate: DateTime(2026, 3, 23),
+      ));
+
+      final result = await db.calendarDao
+          .watchCompletionsInRange(
+            taskId,
+            DateTime(2026, 3, 16),
+            DateTime(2026, 3, 24),
+          )
+          .first;
+      expect(result, isEmpty);
+    });
+
+    test('returns empty list for wrong taskId', () async {
+      final taskId = await db.tasksDao.insertTask(TasksCompanion.insert(
+        roomId: room1Id,
+        name: 'Aufgabe mit Completion',
+        intervalType: IntervalType.weekly,
+        effortLevel: EffortLevel.low,
+        nextDueDate: DateTime(2026, 3, 23),
+      ));
+      // Insert completion for taskId
+      await db.into(db.taskCompletions).insert(TaskCompletionsCompanion.insert(
+        taskId: taskId,
+        completedAt: DateTime(2026, 3, 18),
+      ));
+
+      // Query for a different task ID
+      final result = await db.calendarDao
+          .watchCompletionsInRange(
+            taskId + 999,
+            DateTime(2026, 3, 16),
+            DateTime(2026, 3, 24),
+          )
+          .first;
+      expect(result, isEmpty);
+    });
+
+    test('start is inclusive, end is exclusive', () async {
+      final taskId = await db.tasksDao.insertTask(TasksCompanion.insert(
+        roomId: room1Id,
+        name: 'Grenzen Test',
+        intervalType: IntervalType.weekly,
+        effortLevel: EffortLevel.low,
+        nextDueDate: DateTime(2026, 3, 23),
+      ));
+
+      // Completion exactly at start boundary (inclusive)
+      await db.into(db.taskCompletions).insert(TaskCompletionsCompanion.insert(
+        taskId: taskId,
+        completedAt: DateTime(2026, 3, 16),
+      ));
+      // Completion exactly at end boundary (exclusive — should NOT be included)
+      await db.into(db.taskCompletions).insert(TaskCompletionsCompanion.insert(
+        taskId: taskId,
+        completedAt: DateTime(2026, 3, 24),
+      ));
+
+      final result = await db.calendarDao
+          .watchCompletionsInRange(
+            taskId,
+            DateTime(2026, 3, 16),
+            DateTime(2026, 3, 24),
+          )
+          .first;
+      // Only the start-boundary completion should be included
+      expect(result.length, 1);
+      expect(result.first.completedAt, DateTime(2026, 3, 16));
+    });
+  });
+
   group('CalendarDao.getTaskCountInRoom', () {
     test('returns 0 when room has no tasks', () async {
       final count = await db.calendarDao.getTaskCountInRoom(room1Id);