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>

test/features/tasks/domain/scheduling_test.dart

@@ -0,0 +1,156 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:household_keeper/features/tasks/domain/frequency.dart';
+import 'package:household_keeper/features/tasks/domain/relative_date.dart';
+import 'package:household_keeper/features/tasks/domain/scheduling.dart';
+
+void main() {
+  group('calculateNextDueDate', () {
+    test('daily adds 1 day', () {
+      final result = calculateNextDueDate(
+        currentDueDate: DateTime(2026, 3, 15),
+        intervalType: IntervalType.daily,
+        intervalDays: 1,
+      );
+      expect(result, DateTime(2026, 3, 16));
+    });
+
+    test('everyNDays(3) adds 3 days', () {
+      final result = calculateNextDueDate(
+        currentDueDate: DateTime(2026, 3, 15),
+        intervalType: IntervalType.everyNDays,
+        intervalDays: 3,
+      );
+      expect(result, DateTime(2026, 3, 18));
+    });
+
+    test('weekly adds 7 days', () {
+      final result = calculateNextDueDate(
+        currentDueDate: DateTime(2026, 3, 15),
+        intervalType: IntervalType.weekly,
+        intervalDays: 1,
+      );
+      expect(result, DateTime(2026, 3, 22));
+    });
+
+    test('biweekly adds 14 days', () {
+      final result = calculateNextDueDate(
+        currentDueDate: DateTime(2026, 3, 15),
+        intervalType: IntervalType.biweekly,
+        intervalDays: 1,
+      );
+      expect(result, DateTime(2026, 3, 29));
+    });
+
+    test('monthly from Jan 15 gives Feb 15', () {
+      final result = calculateNextDueDate(
+        currentDueDate: DateTime(2026, 1, 15),
+        intervalType: IntervalType.monthly,
+        intervalDays: 1,
+      );
+      expect(result, DateTime(2026, 2, 15));
+    });
+
+    test('monthly from Jan 31 gives Feb 28 (clamping)', () {
+      final result = calculateNextDueDate(
+        currentDueDate: DateTime(2026, 1, 31),
+        intervalType: IntervalType.monthly,
+        intervalDays: 1,
+      );
+      expect(result, DateTime(2026, 2, 28));
+    });
+
+    test('monthly from Feb 28 (anchor 31) gives Mar 31 (anchor memory)', () {
+      final result = calculateNextDueDate(
+        currentDueDate: DateTime(2026, 2, 28),
+        intervalType: IntervalType.monthly,
+        intervalDays: 1,
+        anchorDay: 31,
+      );
+      expect(result, DateTime(2026, 3, 31));
+    });
+
+    test('quarterly from Jan 15 gives Apr 15', () {
+      final result = calculateNextDueDate(
+        currentDueDate: DateTime(2026, 1, 15),
+        intervalType: IntervalType.quarterly,
+        intervalDays: 1,
+      );
+      expect(result, DateTime(2026, 4, 15));
+    });
+
+    test('yearly from 2026-03-15 gives 2027-03-15', () {
+      final result = calculateNextDueDate(
+        currentDueDate: DateTime(2026, 3, 15),
+        intervalType: IntervalType.yearly,
+        intervalDays: 1,
+      );
+      expect(result, DateTime(2027, 3, 15));
+    });
+
+    test('everyNMonths(2) adds 2 months', () {
+      final result = calculateNextDueDate(
+        currentDueDate: DateTime(2026, 1, 15),
+        intervalType: IntervalType.everyNMonths,
+        intervalDays: 2,
+      );
+      expect(result, DateTime(2026, 3, 15));
+    });
+  });
+
+  group('catchUpToPresent', () {
+    test('skips past occurrences to reach today or future', () {
+      // Task was due Jan 1, weekly interval. Today is Mar 15.
+      // Should advance past all missed weeks to the next week on/after Mar 15.
+      final result = catchUpToPresent(
+        nextDue: DateTime(2026, 1, 1),
+        today: DateTime(2026, 3, 15),
+        intervalType: IntervalType.weekly,
+        intervalDays: 1,
+      );
+      // Jan 1 + 11 weeks = Mar 19 (first Thursday on/after Mar 15)
+      expect(result.isAfter(DateTime(2026, 3, 14)), isTrue);
+      expect(result.isBefore(DateTime(2026, 3, 22)), isTrue);
+    });
+
+    test('returns date unchanged if already in future', () {
+      final futureDate = DateTime(2026, 4, 1);
+      final result = catchUpToPresent(
+        nextDue: futureDate,
+        today: DateTime(2026, 3, 15),
+        intervalType: IntervalType.weekly,
+        intervalDays: 1,
+      );
+      expect(result, futureDate);
+    });
+  });
+
+  group('formatRelativeDate', () {
+    final today = DateTime(2026, 3, 15);
+
+    test('today returns "Heute"', () {
+      expect(formatRelativeDate(DateTime(2026, 3, 15), today), 'Heute');
+    });
+
+    test('tomorrow returns "Morgen"', () {
+      expect(formatRelativeDate(DateTime(2026, 3, 16), today), 'Morgen');
+    });
+
+    test('3 days from now returns "in 3 Tagen"', () {
+      expect(formatRelativeDate(DateTime(2026, 3, 18), today), 'in 3 Tagen');
+    });
+
+    test('1 day overdue returns "Uberfaellig seit 1 Tag"', () {
+      expect(
+        formatRelativeDate(DateTime(2026, 3, 14), today),
+        'Uberfaellig seit 1 Tag',
+      );
+    });
+
+    test('5 days overdue returns "Uberfaellig seit 5 Tagen"', () {
+      expect(
+        formatRelativeDate(DateTime(2026, 3, 10), today),
+        'Uberfaellig seit 5 Tagen',
+      );
+    });
+  });
+}