Accessibility pass: ARIA roles, label associations, CSS class migrations

- Add role=dialog/aria-modal/aria-labelledby to all 12 modal overlays (JS + PHP)
- Add aria-label="Close" to all 14 modal close buttons
- Add full ARIA combobox pattern to @mention autocomplete (listbox, option, aria-selected, aria-expanded)
- Add for= attributes to admin filter form labels (AuditLog, UserActivity, ApiKeys)
- Remove dead closeOnAdvancedSearchBackdropClick() from advanced-search.js

CSS/JS style cleanup:
- Move .ascii-banner static styles from JS inline to CSS class; add .ascii-banner--glow
- Add .ascii-banner-cursor, .loading-overlay--hiding, .has-overlay, tr[data-clickable]
- Add .animate-fadein/.animate-fadeout/.comment--deleting to ticket.css
- Add .lt-toast--hiding to base.css; remove opacity/transition inline JS
- Remove redundant cursor:pointer JS (already in th{} CSS rule)
- Remove trailing space in lt-select class attributes

Bug fixes:
- base.js: boot overlay opacity inline style was overriding .fade-out class opacity via
  specificity (1000 vs 20), preventing the fade-out animation — removed
- ascii-banner.js: cursor used blink-caret (border-color only) instead of blink-cursor
  (opacity-based), so the █ cursor never actually blinked — fixed

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

assets/js/base.js

@@ -124,8 +124,7 @@
   function _dismissToast(toast) {
     if (!toast || !toast.parentNode) return;
     clearTimeout(toast._lt_timer);
-    toast.style.opacity    = '0';
-    toast.style.transition = 'opacity 0.3s ease';
+    toast.classList.add('lt-toast--hiding');
     setTimeout(() => {
       if (toast.parentNode) toast.parentNode.removeChild(toast);
       _toastActive = false;
@@ -176,11 +175,11 @@
        lt.modal.closeAll();
 
      HTML contract:
-       <div id="my-modal-id" class="lt-modal-overlay">
+       <div id="my-modal-id" class="lt-modal-overlay" role="dialog" aria-modal="true" aria-labelledby="myModalTitle">
          <div class="lt-modal">
            <div class="lt-modal-header">
-             <span class="lt-modal-title">Title</span>
-             <button class="lt-modal-close" data-modal-close>✕</button>
+             <span class="lt-modal-title" id="myModalTitle">Title</span>
+             <button class="lt-modal-close" data-modal-close aria-label="Close">✕</button>
            </div>
            <div class="lt-modal-body">…</div>
            <div class="lt-modal-footer">…</div>
@@ -295,7 +294,6 @@
     if (!overlay || !pre) return;
 
     overlay.style.display = 'flex';
-    overlay.style.opacity = '1';
 
     const name      = (appName || 'TERMINAL').toUpperCase();
     const titleStr  = name + ' v1.0';
@@ -653,7 +651,6 @@
 
     const ths = Array.from(table.querySelectorAll('th[data-sort-key]'));
     ths.forEach((th, colIdx) => {
-      th.style.cursor = 'pointer';
       let dir = 'asc';
 
       th.addEventListener('click', () => {