Fix Lyria API response parsing — audio in parts[1], not parts[0]

The Lyria API returns a candidates[].content.parts[] array where:
- parts[0] = text metadata (e.g. '<instrumental>')
- parts[1] = inlineData with the actual audio payload

Previous code only checked parts[0] for inlineData, which always failed
with 'No audio data in response'. Fixed by iterating all parts to find
the inlineData entry.

Successfully generated first real audio clip (lo-fi hip hop, 30s, 728KB MP3).

Also includes: .env.example, requirements updates, docker-compose fixes,
frontend vite config, logger setup.

frontend/vite.config.ts

@@ -7,7 +7,7 @@ export default defineConfig({
     port: 3000,
     proxy: {
       '/api': {
-        target: 'http://localhost:8000',
+        target: 'http://localhost:8100',
         changeOrigin: true,
       }
     }