- Add totalTaskCount field to CalendarDayState to distinguish first-run from celebration
- Add getTaskCount() to CalendarDao (SELECT COUNT from tasks)
- CalendarStrip: 181-day horizontal scroll with German abbreviations, today highlighting, month boundary labels, scroll-to-today controller
- CalendarTaskRow: task name + room tag chip + checkbox, no relative date, isOverdue coral styling
- CalendarDayList: loading/error/first-run-empty/empty-day/celebration/has-tasks states, overdue section (today only), slide-out completion animation
- Update home_screen_test.dart and app_shell_test.dart to test new calendar providers instead of dailyPlanProvider
- CalendarDao.watchTasksForDate: returns tasks due on a specific calendar day, sorted by name
- CalendarDao.watchOverdueTasks: returns tasks due strictly before reference date, sorted by due date
- Registered CalendarDao in AppDatabase @DriftDatabase annotation
- Generated calendar_dao.g.dart and updated database.g.dart
