feat: Add real-time ticket updates via WebSocket and staff permission control

WebSocket Updates:
- Create useTicketWebSocket hook for real-time ticket list updates
- Hook invalidates React Query cache when tickets are created/updated
- Shows toast notifications for new tickets and comments
- Auto-reconnect with exponential backoff

Staff Permissions:
- Add can_access_tickets() method to User model
- Owners and managers always have ticket access
- Staff members need explicit can_access_tickets permission
- Update Sidebar to conditionally show Tickets menu based on permission
- Add can_access_tickets to API user response

Backend Updates:
- Update ticket signals to broadcast updates to all relevant users
- Check ticket access permission in views

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

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

frontend/src/pages/Tickets.tsx

@@ -2,6 +2,7 @@ import React, { useState, useMemo } from 'react';
 import { useTranslation } from 'react-i18next';
 import { Plus, User, Clock, AlertCircle, CheckCircle, XCircle, Circle, Loader2 } from 'lucide-react';
 import { useTickets } from '../hooks/useTickets';
+import { useTicketWebSocket } from '../hooks/useTicketWebSocket';
 import { Ticket, TicketStatus } from '../types';
 import TicketModal from '../components/TicketModal';
 import { useCurrentUser } from '../hooks/useAuth';
@@ -82,6 +83,9 @@ const Tickets: React.FC = () => {
   const [isTicketModalOpen, setIsTicketModalOpen] = useState(false);
   const [selectedTicket, setSelectedTicket] = useState<Ticket | null>(null);
 
+  // Enable real-time ticket updates via WebSocket
+  useTicketWebSocket({ showToasts: true });
+
   // Fetch all tickets (backend will filter based on user role)
   const { data: tickets = [], isLoading, error } = useTickets();