fix(docker): mount config/prompts volumes + add healthcheck

- Mount config/ and prompts/ so users can customize models and prompts
- Add healthcheck using /api/health endpoint
- Use env var for port mapping
- Switch env_file to .env (Docker convention)

Author: PPPPanda

docker-compose.yml

@@ -6,10 +6,18 @@ services:
     container_name: contentpipe
     restart: unless-stopped
     ports:
-      - "8765:8765"
+      - "${CONTENTPIPE_PORT:-8765}:8765"
     env_file:
       - .env
     extra_hosts:
       - "host.docker.internal:host-gateway"
     volumes:
       - ./output:/app/output
+      - ./config:/app/config
+      - ./prompts:/app/prompts
+    healthcheck:
+      test: ["CMD", "python3", "-c", "import httpx; r=httpx.get('http://localhost:8765/api/health'); r.raise_for_status()"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
+      start_period: 15s