feat(02-01): Drift tables, DAOs, scheduling utility, domain models with tests

- Add Rooms, Tasks, TaskCompletions Drift tables with schema v2 migration
- Create RoomsDao with CRUD, watchAll, watchWithStats, cascade delete, reorder
- Create TasksDao with CRUD, watchInRoom (sorted by due), completeTask, overdue detection
- Implement calculateNextDueDate and catchUpToPresent pure scheduling functions
- Define IntervalType enum (8 types), EffortLevel enum, FrequencyInterval model
- Add formatRelativeDate German formatter and curatedRoomIcons icon list
- Enable PRAGMA foreign_keys in beforeOpen migration strategy
- All 30 unit tests passing (17 scheduling + 6 rooms DAO + 7 tasks DAO)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/features/tasks/data/tasks_dao.dart

@@ -0,0 +1,102 @@
+import 'package:drift/drift.dart';
+
+import '../../../core/database/database.dart';
+import '../domain/scheduling.dart';
+
+part 'tasks_dao.g.dart';
+
+@DriftAccessor(tables: [Tasks, TaskCompletions])
+class TasksDao extends DatabaseAccessor<AppDatabase> with _$TasksDaoMixin {
+  TasksDao(super.attachedDatabase);
+
+  /// Watch tasks in a room sorted by nextDueDate ascending.
+  Stream<List<Task>> watchTasksInRoom(int roomId) {
+    return (select(tasks)
+          ..where((t) => t.roomId.equals(roomId))
+          ..orderBy([(t) => OrderingTerm.asc(t.nextDueDate)]))
+        .watch();
+  }
+
+  /// Insert a new task. Returns the auto-generated id.
+  Future<int> insertTask(TasksCompanion task) => into(tasks).insert(task);
+
+  /// Update an existing task. Returns true if a row was updated.
+  Future<bool> updateTask(Task task) => update(tasks).replace(task);
+
+  /// Delete a task and its completions.
+  Future<void> deleteTask(int taskId) {
+    return transaction(() async {
+      await (delete(taskCompletions)..where((c) => c.taskId.equals(taskId)))
+          .go();
+      await (delete(tasks)..where((t) => t.id.equals(taskId))).go();
+    });
+  }
+
+  /// Mark a task as done: records completion and calculates next due date.
+  ///
+  /// Uses scheduling utility for date calculation. Next due is calculated
+  /// from the original due date (not completion date) to keep rhythm stable.
+  /// If the calculated next due is in the past, catch-up advances to present.
+  ///
+  /// [now] parameter allows injection of current time for testing.
+  Future<void> completeTask(int taskId, {DateTime? now}) {
+    return transaction(() async {
+      // 1. Get current task
+      final task =
+          await (select(tasks)..where((t) => t.id.equals(taskId))).getSingle();
+
+      final currentTime = now ?? DateTime.now();
+
+      // 2. Record completion
+      await into(taskCompletions).insert(TaskCompletionsCompanion.insert(
+        taskId: taskId,
+        completedAt: currentTime,
+      ));
+
+      // 3. Calculate next due date (from original due date, not today)
+      var nextDue = calculateNextDueDate(
+        currentDueDate: task.nextDueDate,
+        intervalType: task.intervalType,
+        intervalDays: task.intervalDays,
+        anchorDay: task.anchorDay,
+      );
+
+      // 4. Catch up if next due is still in the past
+      final todayDateOnly = DateTime(
+        currentTime.year,
+        currentTime.month,
+        currentTime.day,
+      );
+      nextDue = catchUpToPresent(
+        nextDue: nextDue,
+        today: todayDateOnly,
+        intervalType: task.intervalType,
+        intervalDays: task.intervalDays,
+        anchorDay: task.anchorDay,
+      );
+
+      // 5. Update task with new due date
+      await (update(tasks)..where((t) => t.id.equals(taskId)))
+          .write(TasksCompanion(nextDueDate: Value(nextDue)));
+    });
+  }
+
+  /// Count overdue tasks in a room (nextDueDate before today).
+  Future<int> getOverdueTaskCount(int roomId, {DateTime? today}) async {
+    final now = today ?? DateTime.now();
+    final todayDateOnly = DateTime(now.year, now.month, now.day);
+
+    final taskList = await (select(tasks)
+          ..where((t) => t.roomId.equals(roomId)))
+        .get();
+
+    return taskList.where((task) {
+      final dueDate = DateTime(
+        task.nextDueDate.year,
+        task.nextDueDate.month,
+        task.nextDueDate.day,
+      );
+      return dueDate.isBefore(todayDateOnly);
+    }).length;
+  }
+}