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/chatai/screenshot.py

@@ -1,6 +1,8 @@
 import asyncio
+import re
 import html as html_module
 import markdown
+import bleach
 from nonebot import logger
 
 async def markdown_to_image(markdown_text: str, output_path: str, browser=None):
@@ -11,6 +13,15 @@ async def markdown_to_image(markdown_text: str, output_path: str, browser=None):
         # Convert markdown to HTML. The markdown library handles special chars safely.
         # Note: do NOT html.escape() before markdown.markdown() - it breaks markdown syntax.
         html_content = markdown.markdown(markdown_text, extensions=["fenced_code", "tables"])
+        # Sanitize to prevent XSS from malicious AI responses
+        allowed_tags = [
+            'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'p', 'br', 'hr',
+            'ul', 'ol', 'li', 'blockquote', 'pre', 'code', 'span',
+            'table', 'thead', 'tbody', 'tr', 'th', 'td',
+            'strong', 'em', 'b', 'i', 'u', 'a', 'img', 'div',
+        ]
+        allowed_attrs = {'a': ['href', 'title'], 'img': ['src', 'alt', 'title']}
+        html_content = bleach.clean(html_content, tags=allowed_tags, attributes=allowed_attrs)
         
         # 使用传入的浏览器实例或创建新的
         if browser is None: