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>

alembic/env.py

@@ -23,7 +23,7 @@ from app.core.database import Base
 
 # Import all models to register them with Base.metadata
 from app.modules.auth.models import UserSession, User
-from app.modules.chat_room.models import IncidentRoom, RoomMember, RoomTemplate
+from app.modules.chat_room.models import IncidentRoom, RoomMember
 from app.modules.realtime.models import Message, MessageReaction, MessageEditHistory
 from app.modules.file_storage.models import RoomFile
 from app.modules.report_generation.models import GeneratedReport