Add Ticket Assignment feature (Feature 2)

- Add assigned_to column support in TicketModel with assignTicket() and unassignTicket() methods
- Create assign_ticket.php API endpoint for assignment operations
- Update TicketController to load user list from UserModel
- Add assignment dropdown UI in TicketView
- Add JavaScript handler for assignment changes
- Integrate with audit log for assignment tracking

Users can now assign tickets to team members via dropdown selector.

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

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

controllers/TicketController.php

@@ -3,17 +3,20 @@
 require_once dirname(__DIR__) . '/models/TicketModel.php';
 require_once dirname(__DIR__) . '/models/CommentModel.php';
 require_once dirname(__DIR__) . '/models/AuditLogModel.php';
+require_once dirname(__DIR__) . '/models/UserModel.php';
 
 class TicketController {
     private $ticketModel;
     private $commentModel;
     private $auditLogModel;
+    private $userModel;
     private $envVars;
     
     public function __construct($conn) {
         $this->ticketModel = new TicketModel($conn);
         $this->commentModel = new CommentModel($conn);
         $this->auditLogModel = new AuditLogModel($conn);
+        $this->userModel = new UserModel($conn);
         
         // Load environment variables for Discord webhook
         $envPath = dirname(__DIR__) . '/.env';
@@ -61,6 +64,9 @@ class TicketController {
         // Get timeline for this ticket
         $timeline = $this->auditLogModel->getTicketTimeline($id);
 
+        // Get all users for assignment dropdown
+        $allUsers = $this->userModel->getAllUsers();
+
         // Load the view
         include dirname(__DIR__) . '/views/TicketView.php';
     }