- Add isActive BoolColumn (default true) to Tasks table
- Bump schema version from 2 to 3 with addColumn migration
- Filter watchTasksInRoom to isActive=true only
- Filter getOverdueTaskCount to isActive=true only
- Add softDeleteTask(taskId) - sets isActive=false without removing data
- Add getCompletionCount(taskId) - counts TaskCompletions for a task
- Add watchCompletionsForTask(taskId) to TasksDao: Stream<List<TaskCompletion>> sorted newest first
- Regenerate tasks_dao.g.dart with build_runner
- Add taskHistoryTitle, taskHistoryEmpty, taskHistoryCount to app_de.arb
- Regenerate app_localizations.dart and app_localizations_de.dart
- All 5 new DAO tests pass, zero analyze issues