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_extensions.py

@@ -0,0 +1,41 @@
+from tinydb import Query
+from db.db import routine_extensions_db
+from models.routine_extension import RoutineExtension
+
+
+def get_extension(child_id: str, routine_id: str, date: str) -> RoutineExtension | None:
+    q = Query()
+    result = routine_extensions_db.search(
+        (q.child_id == child_id) & (q.routine_id == routine_id) & (q.date == date)
+    )
+    if not result:
+        return None
+    return RoutineExtension.from_dict(result[0])
+
+
+def add_extension(extension: RoutineExtension) -> None:
+    routine_extensions_db.insert(extension.to_dict())
+
+
+def delete_extensions_for_child(child_id: str) -> None:
+    q = Query()
+    routine_extensions_db.remove(q.child_id == child_id)
+
+
+def delete_extensions_for_routine(routine_id: str) -> None:
+    q = Query()
+    routine_extensions_db.remove(q.routine_id == routine_id)
+
+
+def delete_extension_for_child_routine(child_id: str, routine_id: str) -> None:
+    q = Query()
+    routine_extensions_db.remove((q.child_id == child_id) & (q.routine_id == routine_id))
+
+
+def get_extension_for_child_routine(child_id: str, routine_id: str) -> RoutineExtension | None:
+    q = Query()
+    results = routine_extensions_db.search((q.child_id == child_id) & (q.routine_id == routine_id))
+    if not results:
+        return None
+    latest = max(results, key=lambda r: r.get('date', ''))
+    return RoutineExtension.from_dict(latest)