feat: add FastAPI token server to pipecat-agent

Adds a lightweight HTTP token server (port 8080) alongside the voice
pipeline so web clients can obtain LiveKit access tokens without a
separate service. Adds fastapi and uvicorn to requirements. Adds
LIVEKIT_PUBLIC_URL env var (wss://voice.hobbs.farm) to docker-compose
so tokens carry the correct public WebSocket URL for browser clients.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -84,6 +84,7 @@ services:
       - SPEECHBRAIN_SERVICE_URL=http://speechbrain-service:8001
       - PIPER_SERVICE_URL=http://piper-tts:8003
       - WHISPER_MODEL=medium
+      - LIVEKIT_PUBLIC_URL=wss://voice.hobbs.farm
     depends_on:
       - livekit-server
       - speechbrain-service