review: fix critical/medium bugs in 4 plugins (round 2)

group_horse_racing:
- settle_race: rewrite with 7 bug fixes (race condition, draw double-credit, empty participants, etc.)
- models.py: reorder fields for correct defaults, add indexes
- message_service: add logger import

danding_points:
- api.py: add finally blocks to 3 methods (add_points, get_history, get_leaderboard)
- database.py: add finally block to get_user_balance

chatai:
- __init__.py: deprecated API→asyncio.to_thread, deduplicate logging, taskkill filter for safety
- screenshot.py: XSS protection with bleach on HTML content
- requirements.txt: add bleach dependency

danding_qqpush:
- api.py L13: fix self-referencing _renderer NameError crash
- api.py: lazy singleton pattern via _get_renderer() instead of per-request ImageRenderer
- __init__.py: mask Token in log output (security)

All 34 tests pass.

danding_bot/plugins/group_horse_racing/message_service.py

@@ -1,9 +1,12 @@
 import asyncio
+import logging
 from typing import Optional, Any
 from nonebot.adapters.onebot.v11 import Bot, Message
 
 from .config import Config
 
+logger = logging.getLogger("horse_racing.message_service")
+
 
 class MessageService:
     def __init__(self, config: Config):