Fix backend bugs: password hash column rename, dynamic import, AuditLog response_model, websocket reference, missing exports, bcrypt version pin

backend/app/services/game_server.py

@@ -236,7 +236,7 @@ async def game_websocket_endpoint(websocket: WebSocket, game_id: int):
                 })
             elif message.get("type") == "ping":
                 # Respond to ping
-                await websocket.send_text(json.dumps({
+                await room.send_to_player(player_id, {
                     "type": "pong",
                     "timestamp": datetime.now().isoformat(),
                 }))
@@ -294,7 +294,7 @@ async def process_game_command(room: GameRoom, player_id: int, command: dict):
         GAME_COMMAND_JUDGE,
         GAME_COMMAND_REVERSE_TURN,
     ]:
-        await websocket.send_text(json.dumps({
+        await room.send_to_player(player_id, {
             "type": "error",
             "message": f"Invalid command type: {cmd_type}",
         }))