Add staff email client with WebSocket real-time updates

Implements a complete email client for platform staff members:

Backend:
- Add routing_mode field to PlatformEmailAddress (PLATFORM/STAFF)
- Create staff_email app with models for folders, emails, attachments, labels
- IMAP service for fetching emails with folder mapping
- SMTP service for sending emails with attachment support
- Celery tasks for periodic sync and full sync operations
- WebSocket consumer for real-time notifications
- Comprehensive API viewsets with filtering and actions

Frontend:
- Thunderbird-style three-pane email interface
- Multi-account support with drag-and-drop ordering
- Email composer with rich text editor
- Email viewer with thread support
- Real-time WebSocket updates for new emails and sync status
- 94 unit tests covering models, serializers, views, services, and consumers

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/hooks/useAuth.ts

@@ -102,11 +102,20 @@ export const useLogout = () => {
       queryClient.removeQueries({ queryKey: ['currentUser'] });
       queryClient.clear();
 
-      // Redirect to login page on root domain
+      // Redirect to appropriate login page based on current subdomain
       const protocol = window.location.protocol;
       const baseDomain = getBaseDomain();
       const port = window.location.port ? `:${window.location.port}` : '';
-      window.location.href = `${protocol}//${baseDomain}${port}/login`;
+      const hostname = window.location.hostname;
+
+      // Check if on platform subdomain
+      if (hostname.startsWith('platform.')) {
+        // Platform users go to platform login page
+        window.location.href = `${protocol}//platform.${baseDomain}${port}/platform/login`;
+      } else {
+        // Business users go to their subdomain's login page
+        window.location.href = `${protocol}//${hostname}${port}/login`;
+      }
     },
   });
 };