revert: simplify listen to PCM-only, remove WebCodecs complexity

- Remove broadcastOpusToWeb from types and webserver
- Revert recorder to PCM-only broadcast path
- Remove WebCodecs AudioDecoder from dashboard.js
- Simplify WebSocket handler to just play PCM frames
- Remove Howler.js and Tone.js dependencies
- Keep simple AudioContext playback that works reliably

package.json

@@ -24,6 +24,7 @@
     "express": "^5.2.1",
     "fluent-ffmpeg": "^2.1.3",
     "helmet": "^8.1.0",
+    "howler": "^2.2.4",
     "libsodium-wrappers": "^0.8.2",
     "p-retry": "^6.2.0",
     "pino": "^9.4.0",
@@ -33,7 +34,6 @@
     "react": "^19.2.6",
     "react-dom": "^19.2.6",
     "sodium-native": "^4.3.2",
-    "tone": "^15.1.22",
     "ws": "^8.20.1",
     "zod": "^4.4.3"
   },