feat(frontend): use Wails bindings for file I/O

Replace hidden file inputs and anchor downloads with native open/save
dialogs via a thin platform layer. WAV export sends base64 audio data to
the Go backend for writing to the user-chosen path.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/vite.config.ts

@@ -4,6 +4,7 @@ import { fileURLToPath } from 'node:url'
 import type { IncomingMessage, ServerResponse } from 'node:http'
 import { defineConfig, type Connect, type Plugin } from 'vite'
 import { svelte } from '@sveltejs/vite-plugin-svelte'
+import wails from '@wailsio/runtime/plugins/vite'
 
 const repoRoot = resolve(fileURLToPath(import.meta.url), '../..')
 const assetsDir = resolve(repoRoot, 'assets')
@@ -49,8 +50,11 @@ function serveRepoAssets(): Plugin {
 }
 
 export default defineConfig({
-  plugins: [svelte(), serveRepoAssets()],
+  plugins: [svelte(), wails('./bindings'), serveRepoAssets()],
   server: {
+    host: '127.0.0.1',
+    port: Number(process.env.WAILS_VITE_PORT) || 5173,
+    strictPort: true,
     fs: {
       allow: [repoRoot],
     },