fix: malformed img tag in header avatar + notif footer inline styles

- Avatar img tag was missing closing > — the endif fired before the tag
  closed, causing the initials span to be parsed as an attribute value;
  this would silently break the avatar fallback when image fails to load
- Replace style="width:100%;text-align:center" on notif footer link with
  lt-w-full lt-text-center utility classes

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

views/layout_header.php

@@ -165,7 +165,7 @@ $_lt_assetVer  = $GLOBALS['config']['ASSET_VERSION'] ?? '20260329';
         <?php if ($_lt_userId > 0): ?>
           <img src="/api/user_avatar.php?user_id=<?= $_lt_userId ?>"
                alt=""
-               class="lt-avatar-img"
+               class="lt-avatar-img">
         <?php endif ?>
         <span class="lt-avatar-initials"><?= htmlspecialchars($_lt_initials) ?></span>
       </div>
@@ -195,7 +195,7 @@ $_lt_assetVer  = $GLOBALS['config']['ASSET_VERSION'] ?? '20260329';
             <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>
+            <a href="/admin/audit-log" class="lt-btn lt-btn-ghost lt-btn-sm lt-w-full lt-text-center">View activity log</a>
           </div>
         </div>
       </div>