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/routine_items.py

@@ -0,0 +1,45 @@
+from tinydb import Query
+from db.db import routine_items_db
+from models.routine_item import RoutineItem
+
+
+def add_item(item: RoutineItem) -> None:
+    routine_items_db.insert(item.to_dict())
+
+
+def get_item(item_id: str) -> RoutineItem | None:
+    q = Query()
+    result = routine_items_db.search(q.id == item_id)
+    if not result:
+        return None
+    return RoutineItem.from_dict(result[0])
+
+
+def get_items_for_routine(routine_id: str) -> list[RoutineItem]:
+    q = Query()
+    results = routine_items_db.search(q.routine_id == routine_id)
+    items = [RoutineItem.from_dict(r) for r in results]
+    return sorted(items, key=lambda i: (i.order, i.created_at))
+
+
+def update_item(item: RoutineItem) -> bool:
+    q = Query()
+    existing = routine_items_db.get(q.id == item.id)
+    if not existing:
+        return False
+    routine_items_db.update(item.to_dict(), q.id == item.id)
+    return True
+
+
+def delete_item(item_id: str) -> bool:
+    q = Query()
+    existing = routine_items_db.get(q.id == item_id)
+    if not existing:
+        return False
+    routine_items_db.remove(q.id == item_id)
+    return True
+
+
+def delete_for_routine(routine_id: str) -> None:
+    q = Query()
+    routine_items_db.remove(q.routine_id == routine_id)