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>

assets/js/settings.js

@@ -131,4 +131,6 @@ document.addEventListener('keydown', (e) => {
 });
 
 // Initialize on page load
-document.addEventListener('DOMContentLoaded', loadUserPreferences);
+document.addEventListener('DOMContentLoaded', function() {
+    if (window.lt) loadUserPreferences();
+});