feat: Implement staff invitation system with role-based permissions

- Add StaffInvitation model with token-based 7-day expiration
- Create invitation API endpoints (create, cancel, resend, accept, decline)
- Add permissions JSONField to User model for granular access control
- Implement frontend invite modal with role-specific permissions:
  - Manager: can_invite_staff, can_manage_resources, can_manage_services,
    can_view_reports, can_access_settings, can_refund_payments
  - Staff: can_view_all_schedules, can_manage_own_appointments
- Add edit staff modal with permissions management and deactivate option
- Create AcceptInvitePage for invitation acceptance flow
- Add active/inactive staff separation with collapsible section
- Auto-create bookable resource when configured at invite time
- Remove Quick Add Appointment from dashboard

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

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

frontend/src/hooks/useAuth.ts

@@ -15,6 +15,20 @@ import {
 } from '../api/auth';
 import { getCookie, setCookie, deleteCookie } from '../utils/cookies';
 
+/**
+ * Helper hook to set auth tokens (used by invitation acceptance)
+ */
+export const useAuth = () => {
+  const queryClient = useQueryClient();
+
+  const setTokens = (accessToken: string, refreshToken: string) => {
+    setCookie('access_token', accessToken, 7);
+    setCookie('refresh_token', refreshToken, 7);
+  };
+
+  return { setTokens };
+};
+
 /**
  * Hook to get current user
  */