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/shared.py

@@ -132,6 +132,21 @@ def _describe_points_delta(delta: int) -> str:
     return "略有损失"
 
 
+async def _is_admin_or_owner(bot: Bot, event: Event) -> bool:
+    """Check if the event sender is a group admin or owner."""
+    if not isinstance(event, GroupMessageEvent):
+        return False
+    try:
+        member_info = await bot.get_group_member_info(
+            group_id=event.group_id,
+            user_id=int(event.get_user_id()),
+        )
+        return member_info.get("role", "") in ("admin", "owner")
+    except Exception:
+        return False
+
+
+
 def _build_point_changes(room: Room, odds: dict[str, float]) -> tuple[dict[str, int], dict[str, str]]:
     point_changes: dict[str, int] = {}