fix: Cache busting and visibility group editing UI

- Add cache busting query params to JS/CSS files (v=20260123)
- Add visibility group selection UI for editing existing tickets
- Add toggleVisibilityGroupsEdit() and getSelectedVisibilityGroups() functions
- Fix visibility data being saved when editing tickets
- Pass $conn to views for UserModel access

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

controllers/TicketController.php

@@ -80,10 +80,13 @@ class TicketController {
         // Get allowed status transitions for this ticket
         $allowedTransitions = $this->workflowModel->getAllowedTransitions($ticket['status']);
 
+        // Make $conn available to view for visibility groups
+        $conn = $this->conn;
+
         // Load the view
         include dirname(__DIR__) . '/views/TicketView.php';
     }
-    
+
     public function create() {
         // Get current user
         $currentUser = $GLOBALS['currentUser'] ?? null;