fix(voice-gateway): S2S idle timeout + upstream send lock + iOS AudioContext suspended + port 3012→3013

- P0: S2S DialogAudioIdleTimeoutError now notifies client instead of force-closing, sets upstreamReady=false and cancels keepalive
- P0: Reduce audioKeepaliveIntervalMs from 20s to 8s to prevent S2S idle timeout
- P1: Add upstreamSendLock to prevent concurrent IllegalStateException: Send pending
- P1: iOS AudioContext suspended handling - buffer audio chunks and try resume after user interaction
- P1: disconnect() clears pendingAudioChunks and _resuming to prevent memory leak
- Fix: Frontend hardcoded port 3012→3013 in videoApi.js and vite.config.js
- Add complete Java backend source code to git tracking

delivery/client/vite.config.js

@@ -0,0 +1,27 @@
+import { defineConfig } from 'vite';
+import react from '@vitejs/plugin-react';
+import tailwindcss from '@tailwindcss/vite';
+
+const backendTarget = 'http://localhost:3013';
+
+export default defineConfig({
+  plugins: [react(), tailwindcss()],
+  build: {
+    outDir: 'dist',
+    sourcemap: false,
+  },
+  server: {
+    port: 5174,
+    proxy: {
+      '/api': {
+        target: backendTarget,
+        changeOrigin: true,
+      },
+      '/ws': {
+        target: backendTarget,
+        changeOrigin: true,
+        ws: true,
+      },
+    },
+  },
+});