Fix after merge

backend/src/state.py

@@ -1,4 +1,4 @@
-from dataclasses import dataclass
+from dataclasses import dataclass, field
 from sqlite3 import Cursor
 
 from flask import Flask
@@ -10,4 +10,4 @@ from .room import Room
 class State:
     app: Flask
     db: Cursor
-    rooms: dict[int, Room] = {}  # { room_id: room, ... }
+    rooms: dict[int, Room] = field(default_factory=dict)  # { room_id: room, ... }