Fix JS SyntaxError breaking tabs, textarea scrolling, and XSS escaping

Bug fixes:
- ticket.js: Remove duplicate const textarea declaration inside showMentionSuggestions()
  (was redeclaring a parameter, causing SyntaxError that broke all tab switching)
- ticket.css: Add overflow:hidden + resize:none to disabled textarea so description
  shows full height without internal scrollbar (page scrolls instead)
- ticket.js: Trigger height recalculation when entering edit mode on description

XSS/escaping fixes:
- TicketView.php: htmlspecialchars() on description textarea content (closes </textarea> injection risk)
- TicketView.php: htmlspecialchars() on ticket status and workflow transition status strings
- DashboardView.php: htmlspecialchars() on $cat/$type in input value= attributes
- RecurringTicketsView.php: htmlspecialchars() on composed schedule string

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

views/admin/RecurringTicketsView.php

@@ -81,7 +81,7 @@ $nonce = SecurityHeadersMiddleware::getNonce();
                                             $schedule .= ' (Day ' . $rt['schedule_day'] . ')';
                                         }
                                         $schedule .= ' @ ' . substr($rt['schedule_time'], 0, 5);
-                                        echo $schedule;
+                                        echo htmlspecialchars($schedule);
                                         ?>
                                     </td>
                                     <td><?php echo htmlspecialchars($rt['category']); ?></td>