feat: SLA live timer, notification bell, lt-toggle MD, right drawer, kanban drag-drop

- TicketView: SLA banner now shows live HH:MM:SS elapsed + countdown via JS setInterval
  (previously showed static hours from PHP)
- TicketView: Markdown toggles in comment form replaced with lt-toggle switches
- layout_header: In-app notification bell (🔔) with dropdown panel for all users
- layout_footer: Notification JS — polls /api/notifications.php every 60s, badge count,
  mark-all-read, panel open/close with Escape/outside-click
- api/notifications.php (new): Returns assign/comment/status-change events from audit_log
  for current user's tickets and watched tickets; mark-read via user_preferences
- DashboardView: Ticket preview right drawer — Ctrl+click title or ⊙ peek button
  opens lt-drawer-right with ticket summary extracted from table row DOM
- DashboardView: lt.sortable wired on all 4 kanban columns (group='kanban')
  Cross-column drag = status change via POST /api/update_ticket.php with optimistic UI

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

views/layout_header.php

@@ -174,6 +174,32 @@ $_lt_assetVer  = $GLOBALS['config']['ASSET_VERSION'] ?? '20260329';
 <?php   if ($_lt_isAdmin): ?>
       <span class="lt-badge lt-badge-admin" aria-label="Administrator">ADMIN</span>
 <?php   endif; ?>
+<?php endif; ?>
+      <!-- Notification Bell -->
+<?php if (!empty($_lt_user)): ?>
+      <div class="lt-notif-dropdown-wrap" id="lt-notif-wrap">
+        <button type="button"
+                class="lt-btn lt-btn-ghost lt-btn-sm lt-notif-wrap"
+                id="lt-notif-bell"
+                aria-label="Notifications"
+                aria-expanded="false"
+                aria-controls="lt-notif-panel"
+                title="Notifications">
+          &#x1F514;
+        </button>
+        <div class="lt-notif-panel" id="lt-notif-panel" aria-hidden="true" role="dialog" aria-label="Notifications">
+          <div class="lt-notif-panel-header">
+            <span>Notifications</span>
+            <button type="button" class="lt-notif-panel-clear" id="lt-notif-clear-btn">Mark all read</button>
+          </div>
+          <div class="lt-notif-panel-list" id="lt-notif-list">
+            <div style="padding:0.75rem;font-size:0.75rem;color:var(--text-muted);text-align:center">Loading&hellip;</div>
+          </div>
+          <div class="lt-notif-panel-footer">
+            <a href="/admin/audit-log" class="lt-btn lt-btn-ghost lt-btn-sm" style="width:100%;text-align:center">View activity log</a>
+          </div>
+        </div>
+      </div>
 <?php endif; ?>
       <button type="button" class="lt-theme-btn" id="lt-theme-btn"
               aria-label="Switch to light mode" title="Switch to light mode">&#x2600;</button>