feat: Implement keyboard shortcuts system with UI management, add txt-to-pdf tests, and introduce a generic warning modal.

src/js/utils/shortcuts-init.ts

@@ -0,0 +1,7 @@
+import { ShortcutsManager } from '../logic/shortcuts.js';
+
+export function initializeGlobalShortcuts() {
+    ShortcutsManager.init();
+
+    console.log('Global shortcuts initialized');
+}