cache-bust: add filemtime-based versioning to all CSS and JS assets

templates/admin/footer.php

@@ -1,5 +1,5 @@
 <?php foreach ($extraJs ?? [] as $js): ?>
-<script src="<?= htmlspecialchars($js) ?>"></script>
+<script src="<?= App::assetV($js) ?>"></script>
 <?php endforeach; ?>
 <?php if (!empty($extraJsInline)): ?>
 <script><?= $extraJsInline ?></script>