fix(ticketing): restrict settings link to admins and protect global priorities

- Show 'Go to Settings' bootstrap link only for admin/super_admin users
- Pass isSiteAdmin prop to Create.vue to control settings CTA visibility
- Require site admin for updatePriority/destroyPriority when priority is global (group_id = null)
- Closes: non-admin users seeing forbidden settings link; agents mutating global priorities

src/Http/Controllers/TicketController.php

@@ -242,6 +242,7 @@ class TicketController extends Controller
                 'groups' => [],
                 'priorities' => [],
                 'isBootstrap' => true,
+                'isSiteAdmin' => in_array(Auth::user()->role ?? '', ['admin', 'super_admin']),
             ]);
         }
 
@@ -255,6 +256,7 @@ class TicketController extends Controller
             'groups' => $groups,
             'priorities' => $priorities,
             'isBootstrap' => false,
+            'isSiteAdmin' => in_array(Auth::user()->role ?? '', ['admin', 'super_admin']),
         ]);
     }