Guard lt.* calls when base.js unavailable to prevent crash

Wraps all lt.keys.initDefaults() calls in `if (window.lt)` guards across
6 view files. Adds `if (!window.lt) return` bail-out in keyboard-shortcuts.js
and `if (window.lt)` guard in settings.js DOMContentLoaded handler.

This prevents TypeError crashes when /web_template/base.js returns 404,
which was causing the admin menu click delegation to never register.

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

views/DashboardView.php

@@ -854,7 +854,7 @@ $nonce = SecurityHeadersMiddleware::getNonce();
     <script nonce="<?php echo $nonce; ?>" src="<?php echo $GLOBALS['config']['ASSETS_URL']; ?>/js/advanced-search.js"></script>
     <script nonce="<?php echo $nonce; ?>">
         // Initialize lt keyboard defaults (ESC closes modals, Ctrl+K focuses search, ? shows help)
-        lt.keys.initDefaults();
+        if (window.lt) lt.keys.initDefaults();
         // Event delegation for all data-action handlers
         document.addEventListener('click', function(event) {
             const target = event.target.closest('[data-action]');