refactor: extract admin check helper & harden room_store JSON parsing

- Extract duplicated admin/owner check from race.py into shared._is_admin_or_owner()
- Add try/except around JSON.loads in room_store.load_rooms for corrupted data resilience
- Use .get() for safer dict access in room deserialization

danding_bot/plugins/group_horse_racing/commands/race.py

@@ -7,6 +7,7 @@ from .shared import (
     _send_to_scope, _build_race_image_message,
     _get_user_name, _get_horses_in_order, _format_horse_label,
     run_race_with_settlement, points_service,
+    _is_admin_or_owner,
 )
 from ..models import RoomState, HorseState
 
@@ -64,17 +65,7 @@ async def handle_start(bot: Bot, event: Event):
             return
 
         is_participant = user_id in [h.owner_id for h in room.horses.values()]
-        is_admin = False
-        if isinstance(event, GroupMessageEvent):
-            try:
-                member_info = await bot.get_group_member_info(
-                    group_id=event.group_id, 
-                    user_id=int(user_id)
-                )
-                role = member_info.get("role", "")
-                is_admin = role in ("admin", "owner")
-            except Exception:
-                pass
+        is_admin = await _is_admin_or_owner(bot, event)
         
         if not is_participant and not is_admin:
             await start_cmd.finish("只有参赛者或群管理员可以开赛")
@@ -114,17 +105,7 @@ async def handle_cancel_race(bot: Bot, event: Event):
             return
 
         is_participant = user_id in [h.owner_id for h in room.horses.values()]
-        is_admin = False
-        if isinstance(event, GroupMessageEvent):
-            try:
-                member_info = await bot.get_group_member_info(
-                    group_id=event.group_id,
-                    user_id=int(user_id)
-                )
-                role = member_info.get("role", "")
-                is_admin = role in ("admin", "owner")
-            except Exception:
-                pass
+        is_admin = await _is_admin_or_owner(bot, event)
 
         if not is_participant and not is_admin:
             await cancel_race_cmd.finish("只有参赛者或群管理员可以取消比赛")