docs: document patent PDF volume mount for containerized deployments

Switch docker-compose.yml from bind mount to a named volume (patent_data)
so downloaded PDFs survive container recreation. Add a "Patent PDF Storage"
section to DEPLOYMENT.md covering Docker Compose, Kubernetes PVC, and S3
alternatives.

Closes leeworks-agents/SPARC#1360

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -49,7 +49,7 @@ services:
       init-db:
         condition: service_completed_successfully
     volumes:
-      - ./patents:/app/patents
+      - patent_data:/app/patents
     restart: unless-stopped
 
   # Optional: MinIO for S3-compatible local object storage
@@ -86,4 +86,5 @@ services:
 
 volumes:
   postgres_data:
+  patent_data:
   minio_data: