fix: CSS nesting conflict, dashboard.js dead code removal, admin view escaping

CSS:
- ticket.css: use combined .comment.thread-depth-N selectors to resolve the
  margin-left conflict between .comment-reply and .thread-depth-N classes

dashboard.js:
- Remove legacy initStatusFilter() (superseded by TDS v1.2 sidebar filters)
- Remove initTableSorting() call (client-side sort conflicts with server ?sort=)
- Remove quickSave() + saveTicket() (old hamburger-menu ticket page functions)
- Remove global loadTemplate() (duplicate of IIFE-scoped version in CreateTicketView)
- Remove generateSkeletonRows/Comments/Stats helpers (never called, used
  unregistered CSS class names like .skeleton-row-tr)
- Remove "force dark mode" lines that overrode the user theme preference
- Fix non-TDS CSS classes in modal templates: text-center → style, text-green →
  lt-text-cyan, mb-half → lt-mb-xs, modal-warning-text → lt-text-danger

Admin views:
- RecurringTicketsView: replace innerHTML += loop with createElement/appendChild
  (avoids serial DOM re-parsing on each iteration)
- AuditLogView: add htmlspecialchars() to action_type option values (consistency)

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

views/admin/AuditLogView.php

@@ -29,7 +29,7 @@ include __DIR__ . '/../../views/layout_header.php';
         <select name="action_type" id="action_type" class="lt-select lt-select-sm">
           <option value="">All Actions</option>
           <?php foreach (['create','update','delete','comment','assign','status_change','login','security'] as $a): ?>
-            <option value="<?= $a ?>" <?= ($filters['action_type'] ?? '') === $a ? 'selected' : '' ?>><?= ucfirst(str_replace('_',' ',$a)) ?></option>
+            <option value="<?= htmlspecialchars($a, ENT_QUOTES, 'UTF-8') ?>" <?= ($filters['action_type'] ?? '') === $a ? 'selected' : '' ?>><?= htmlspecialchars(ucfirst(str_replace('_', ' ', $a)), ENT_QUOTES, 'UTF-8') ?></option>
           <?php endforeach ?>
         </select>
       </div>