feat: add create and delete file/folder functionality to editor

- Add Tauri backend commands: create_file, create_directory, delete_file, delete_directory
- Add editor store functions for create/delete with auto-refresh
- Add FileContextMenu component with right-click support
- Add InputDialog component for file/folder name input
- Add ConfirmDialog component for delete confirmation
- Add Ctrl+N keyboard shortcut for new file
- Update keyboard shortcuts modal with new shortcuts
- Auto-close tabs when their files are deleted
- Auto-refresh file tree after create/delete operations

src/routes/+page.svelte

@@ -238,6 +238,15 @@
       }
       return;
     }
+
+    // Ctrl+N - New file (when editor is visible)
+    // Note: This just emits an event that FileBrowser listens to
+    if (event.ctrlKey && event.key === "n" && get(editorStore.isEditorVisible)) {
+      event.preventDefault();
+      // Dispatch a custom event that FileBrowser will listen to
+      window.dispatchEvent(new CustomEvent("editor-new-file"));
+      return;
+    }
   }
 
   async function handleInterrupt() {