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>

assets/css/ticket.css

@@ -584,6 +584,8 @@ textarea.editable {
     background: var(--bg-secondary);
     cursor: default;
     border-color: transparent;
+    overflow: hidden;
+    resize: none;
 }
 
 /* Button Styles */