refactor: Modularize UI components and utilities

- Extract UI components into separate JS files
- Centralize configuration values in config.js
- Introduce a dedicated logger module
- Improve file tree drag-and-drop and undo functionality
- Refactor modal handling to a single manager
- Add URL routing support for SPA navigation
- Implement view mode for read-only access

static/js/notification-service.js

@@ -0,0 +1,77 @@
+/**
+ * Notification Service
+ * Provides a standardized way to show toast notifications
+ * Wraps the showNotification function from ui-utils.js
+ */
+
+class NotificationService {
+    /**
+     * Show a success notification
+     * @param {string} message - The message to display
+     */
+    static success(message) {
+        if (window.showNotification) {
+            window.showNotification(message, Config.NOTIFICATION_TYPES.SUCCESS);
+        } else {
+            Logger.warn('showNotification not available, falling back to console');
+            console.log(`✅ ${message}`);
+        }
+    }
+
+    /**
+     * Show an error notification
+     * @param {string} message - The message to display
+     */
+    static error(message) {
+        if (window.showNotification) {
+            window.showNotification(message, Config.NOTIFICATION_TYPES.ERROR);
+        } else {
+            Logger.warn('showNotification not available, falling back to console');
+            console.error(`❌ ${message}`);
+        }
+    }
+
+    /**
+     * Show a warning notification
+     * @param {string} message - The message to display
+     */
+    static warning(message) {
+        if (window.showNotification) {
+            window.showNotification(message, Config.NOTIFICATION_TYPES.WARNING);
+        } else {
+            Logger.warn('showNotification not available, falling back to console');
+            console.warn(`⚠️ ${message}`);
+        }
+    }
+
+    /**
+     * Show an info notification
+     * @param {string} message - The message to display
+     */
+    static info(message) {
+        if (window.showNotification) {
+            window.showNotification(message, Config.NOTIFICATION_TYPES.INFO);
+        } else {
+            Logger.warn('showNotification not available, falling back to console');
+            console.info(`ℹ️ ${message}`);
+        }
+    }
+
+    /**
+     * Show a notification with a custom type
+     * @param {string} message - The message to display
+     * @param {string} type - The notification type (success, danger, warning, primary, etc.)
+     */
+    static show(message, type = 'primary') {
+        if (window.showNotification) {
+            window.showNotification(message, type);
+        } else {
+            Logger.warn('showNotification not available, falling back to console');
+            console.log(`[${type.toUpperCase()}] ${message}`);
+        }
+    }
+}
+
+// Make NotificationService globally available
+window.NotificationService = NotificationService;
+