chore(infra): remove static_books volume from scraper service

No longer needed — chapters and audio are stored in MinIO, metadata in
PocketBase. The legacy filesystem writer is not used in production.

docker-compose.yml

@@ -124,7 +124,6 @@ services:
       BROWSERLESS_STRATEGY: "${BROWSERLESS_STRATEGY:-direct}"
       # 0 → defaults to NumCPU inside the container.
       SCRAPER_WORKERS: "${SCRAPER_WORKERS:-0}"
-      SCRAPER_STATIC_ROOT: "/app/static/books"
       SCRAPER_HTTP_ADDR: ":8080"
       LOG_LEVEL: "debug"
       # Kokoro-FastAPI TTS endpoint.
@@ -143,8 +142,6 @@ services:
       POCKETBASE_ADMIN_PASSWORD: "${POCKETBASE_ADMIN_PASSWORD:-changeme123}"
     ports:
       - "${SCRAPER_PORT:-8080}:8080"
-    volumes:
-      - static_books:/app/static/books
     healthcheck:
       test: ["CMD", "wget", "-qO-", "http://localhost:8080/health"]
       interval: 15s
@@ -180,6 +177,5 @@ services:
       retries: 3
 
 volumes:
-  static_books:
   minio_data:
   pb_data: