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/report_generation/schemas.py

@@ -67,6 +67,13 @@ class ReportListResponse(BaseModel):
     total: int
 
 
+class ReportMarkdownResponse(BaseModel):
+    """Report content in Markdown format for in-page preview"""
+    report_id: str
+    report_title: Optional[str] = None
+    markdown: str = Field(..., description="Full report content in Markdown format")
+
+
 # AI Report Content Schemas (validated JSON from DIFY)
 class TimelineEvent(BaseModel):
     """Single event in timeline"""
@@ -103,3 +110,10 @@ class AIReportContent(BaseModel):
 class ErrorResponse(BaseModel):
     """Error response"""
     detail: str
+
+
+# Health Check Response
+class HealthCheckResponse(BaseModel):
+    """DIFY service health check response"""
+    status: str = Field(..., description="Status: 'ok' or 'error'")
+    message: str = Field(..., description="Human-readable status message")