feat: Add Chat UX improvements with notifications and @mention support

- Add ActionBar component with expandable toolbar for mobile
- Add @mention functionality with autocomplete dropdown
- Add browser notification system (push, sound, vibration)
- Add NotificationSettings modal for user preferences
- Add mention badges on room list cards
- Add ReportPreview with Markdown rendering and copy/download
- Add message copy functionality with hover actions
- Add backend mentions field to messages with Alembic migration
- Add lots field to rooms, remove templates
- Optimize WebSocket database session handling
- Various UX polish (animations, accessibility)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

app/modules/auth/middleware.py

@@ -26,6 +26,10 @@ class AuthMiddleware:
     async def __call__(self, request: Request, call_next):
         """Process request through authentication checks"""
 
+        # Skip auth for CORS preflight requests (OPTIONS)
+        if request.method == "OPTIONS":
+            return await call_next(request)
+
         # Skip auth for non-API routes (frontend), login/logout, and docs
         path = request.url.path
         if not path.startswith("/api") or path in ["/api/auth/login", "/api/auth/logout", "/api/health"]: