feat: Implement routines feature with CRUD operations and child assignment

- Add backend routines management with add, get, update, delete, and list functionalities.
- Create models for Routine, RoutineItem, RoutineSchedule, and RoutineExtension.
- Develop event types for routine confirmation and modification.
- Implement frontend components for routine assignment, confirmation dialog, and routine management views.
- Add unit tests for routine API and integration tests for routine CRUD flow.
- Create end-to-end test plan for routines feature covering parent and child interactions.

backend/db/routines.py

@@ -0,0 +1,39 @@
+from tinydb import Query
+from db.db import routine_db
+from models.routine import Routine
+
+
+def add_routine(routine: Routine) -> None:
+    routine_db.insert(routine.to_dict())
+
+
+def get_routine(routine_id: str) -> Routine | None:
+    q = Query()
+    result = routine_db.search(q.id == routine_id)
+    if not result:
+        return None
+    return Routine.from_dict(result[0])
+
+
+def update_routine(routine: Routine) -> bool:
+    q = Query()
+    existing = routine_db.get(q.id == routine.id)
+    if not existing:
+        return False
+    routine_db.update(routine.to_dict(), q.id == routine.id)
+    return True
+
+
+def delete_routine(routine_id: str) -> bool:
+    q = Query()
+    existing = routine_db.get(q.id == routine_id)
+    if not existing:
+        return False
+    routine_db.remove(q.id == routine_id)
+    return True
+
+
+def list_routines_for_user(user_id: str) -> list[Routine]:
+    q = Query()
+    results = routine_db.search((q.user_id == user_id) | (q.user_id == None))
+    return [Routine.from_dict(r) for r in results]