feat(07-01): integrate sort logic into calendarDayProvider and tasksInRoomProvider

- calendarDayProvider watches sortPreferenceProvider and sorts dayTasks
- overdueTasks intentionally unsorted (pinned at top per design decision)
- tasksInRoomProvider watches sortPreferenceProvider and sorts via stream.map
- _sortTasks helper (TaskWithRoom) and _sortTasksRaw helper (Task) both support:
  - alphabetical: case-insensitive A-Z by name
  - interval: by intervalType.index ascending, intervalDays as tiebreaker
  - effort: by effortLevel.index ascending (low→medium→high)
- All 113 tests pass, analyze clean

lib/features/home/presentation/calendar_providers.dart

@@ -3,6 +3,8 @@ 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/task_sort_option.dart';
+import 'package:household_keeper/features/tasks/presentation/sort_preference_notifier.dart';
 
 /// Notifier that manages the currently selected date in the calendar strip.
 ///
@@ -27,17 +29,52 @@ final selectedDateProvider =
   SelectedDateNotifier.new,
 );
 
+/// Sort a list of [TaskWithRoom] by the given [sortOption].
+///
+/// Returns a new sorted list; never mutates the original.
+/// Only [dayTasks] are sorted — the overdue section stays in its existing
+/// order per user decision.
+List<TaskWithRoom> _sortTasks(
+  List<TaskWithRoom> tasks,
+  TaskSortOption sortOption,
+) {
+  final sorted = List<TaskWithRoom>.from(tasks);
+  switch (sortOption) {
+    case TaskSortOption.alphabetical:
+      sorted.sort((a, b) => a.task.name.toLowerCase().compareTo(
+            b.task.name.toLowerCase(),
+          ));
+    case TaskSortOption.interval:
+      sorted.sort((a, b) {
+        final cmp = a.task.intervalType.index.compareTo(
+          b.task.intervalType.index,
+        );
+        if (cmp != 0) return cmp;
+        return a.task.intervalDays.compareTo(b.task.intervalDays);
+      });
+    case TaskSortOption.effort:
+      sorted.sort((a, b) => a.task.effortLevel.index.compareTo(
+            b.task.effortLevel.index,
+          ));
+  }
+  return sorted;
+}
+
 /// Reactive calendar day state: tasks for the selected date + overdue tasks.
 ///
 /// 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).
+///
 /// Defined manually (not @riverpod) because riverpod_generator has trouble
 /// with drift's generated [Task] type. Same pattern as [dailyPlanProvider].
 final calendarDayProvider =
     StreamProvider.autoDispose<CalendarDayState>((ref) {
   final db = ref.watch(appDatabaseProvider);
   final selectedDate = ref.watch(selectedDateProvider);
+  final sortOption = ref.watch(sortPreferenceProvider);
 
   final now = DateTime.now();
   final today = DateTime(now.year, now.month, now.day);
@@ -61,7 +98,7 @@ final calendarDayProvider =
 
     return CalendarDayState(
       selectedDate: selectedDate,
-      dayTasks: dayTasks,
+      dayTasks: _sortTasks(dayTasks, sortOption),
       overdueTasks: overdueTasks,
       totalTaskCount: totalTaskCount,
     );

lib/features/tasks/presentation/task_providers.dart

@@ -6,17 +6,44 @@ import 'package:household_keeper/core/database/database.dart';
 import 'package:household_keeper/core/providers/database_provider.dart';
 import 'package:household_keeper/features/tasks/domain/effort_level.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';
 
 part 'task_providers.g.dart';
 
-/// Stream provider family for tasks in a specific room, sorted by due date.
+/// Sort a list of [Task] by the given [sortOption].
+///
+/// Returns a new sorted list; never mutates the original.
+List<Task> _sortTasksRaw(List<Task> tasks, TaskSortOption sortOption) {
+  final sorted = List<Task>.from(tasks);
+  switch (sortOption) {
+    case TaskSortOption.alphabetical:
+      sorted.sort((a, b) => a.name.toLowerCase().compareTo(
+            b.name.toLowerCase(),
+          ));
+    case TaskSortOption.interval:
+      sorted.sort((a, b) {
+        final cmp = a.intervalType.index.compareTo(b.intervalType.index);
+        if (cmp != 0) return cmp;
+        return a.intervalDays.compareTo(b.intervalDays);
+      });
+    case TaskSortOption.effort:
+      sorted.sort((a, b) => a.effortLevel.index.compareTo(b.effortLevel.index));
+  }
+  return sorted;
+}
+
+/// Stream provider family for tasks in a specific room, sorted by active sort preference.
 ///
 /// Defined manually because riverpod_generator has trouble with drift's
 /// generated [Task] type in family provider return types.
 final tasksInRoomProvider =
     StreamProvider.family.autoDispose<List<Task>, int>((ref, roomId) {
   final db = ref.watch(appDatabaseProvider);
-  return db.tasksDao.watchTasksInRoom(roomId);
+  final sortOption = ref.watch(sortPreferenceProvider);
+  return db.tasksDao
+      .watchTasksInRoom(roomId)
+      .map((tasks) => _sortTasksRaw(tasks, sortOption));
 });
 
 /// Notifier for task mutations: create, update, delete, complete.