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>

docs/DEPLOYMENT.md

@@ -276,7 +276,7 @@ The `docker-compose.yml` includes all services needed for production:
 |---------|-----------|------|-------------|
 | `postgres` | sparc-postgres | 5432 | PostgreSQL database |
 | `init-db` | sparc-init-db | - | One-time database initialization (seeds admin user) |
-| `api` | sparc-api | 8000 | FastAPI REST API with JWT auth |
+| `api` | sparc-api | 8000 | FastAPI REST API with JWT auth (patent PDFs stored in `patent_data` volume) |
 | `dashboard` | sparc-dashboard | 8080 | React TypeScript web UI |
 
 ### Common Docker Compose Commands
@@ -307,6 +307,81 @@ docker-compose restart api
 
 ---
 
+## Patent PDF Storage
+
+The SPARC API downloads patent PDFs during analysis and stores them at `/app/patents` inside the container. These files are used for subsequent single-patent analysis requests and as a local cache to avoid re-downloading. If this directory is not persisted, all downloaded PDFs are lost when the container is recreated.
+
+### Docker Compose (default)
+
+The default `docker-compose.yml` declares a named volume called `patent_data` that is mounted at `/app/patents`:
+
+```yaml
+# In the api service:
+volumes:
+  - patent_data:/app/patents
+
+# At the top-level volumes section:
+volumes:
+  patent_data:
+```
+
+This means PDFs survive `docker compose down` and `docker compose up` cycles. To remove patent data intentionally, run:
+
+```bash
+docker compose down -v   # WARNING: also removes postgres_data
+# or selectively:
+docker volume rm sparc_patent_data
+```
+
+If you prefer a bind mount (e.g., for easy host-side access during development), replace the volume with:
+
+```yaml
+volumes:
+  - ./patents:/app/patents
+```
+
+### Kubernetes
+
+For Kubernetes deployments, create a PersistentVolumeClaim and mount it into the API pod:
+
+```yaml
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: sparc-patent-data
+spec:
+  accessModes:
+    - ReadWriteOnce
+  resources:
+    requests:
+      storage: 5Gi
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: sparc-api
+spec:
+  template:
+    spec:
+      containers:
+        - name: api
+          volumeMounts:
+            - name: patent-data
+              mountPath: /app/patents
+      volumes:
+        - name: patent-data
+          persistentVolumeClaim:
+            claimName: sparc-patent-data
+```
+
+Adjust the storage size based on expected patent volume. Each patent PDF is typically 1-5 MB.
+
+### S3 Object Storage (alternative)
+
+For production deployments that need shared or highly durable storage, set `STORAGE_BACKEND=s3` in your `.env` file. This stores patent PDFs in an S3-compatible bucket (AWS S3 or MinIO) instead of the local filesystem, eliminating the need for a persistent volume. See the S3/MinIO section in `.env.example` for configuration details.
+
+---
+
 ## Troubleshooting
 
 ### Database Connection Issues