trying to fix export issue and waveform load

frontend/src/vite-env.d.ts

@@ -1,5 +1,13 @@
 /// <reference types="vite/client" />
 
+interface ImportMetaEnv {
+  readonly VITE_BACKEND_PORT?: string;
+}
+
+interface ImportMeta {
+  readonly env: ImportMetaEnv;
+}
+
 interface DesktopAPI {
   openFile: (options?: Record<string, unknown>) => Promise<string | null>;
   saveFile: (options?: Record<string, unknown>) => Promise<string | null>;