Document bind-mount permissions and ignore runtime data tree

doc/operations-and-configuration.md

@@ -42,6 +42,22 @@ Tail logs:
 docker compose logs -f
 ```
 
+## Host Bind Mounts
+
+If you replace Docker named volumes with host bind mounts (for example `./data/storage:/data/storage`), ensure host directories exist and are writable by the backend runtime user.
+
+Backend and worker run as non-root user `uid=10001` inside containers. For host-mounted storage paths:
+
+```bash
+mkdir -p ./data/storage
+sudo chown -R 10001:10001 ./data/storage
+sudo chmod -R u+rwX,g+rwX ./data/storage
+```
+
+If permissions are incorrect, API startup fails with errors similar to:
+- `PermissionError: [Errno 13] Permission denied: '/data/storage'`
+- `FileNotFoundError` for `/data/storage/originals`
+
 ## Frontend Build Baseline
 
 The frontend Dockerfile uses `node:22-slim` with a standard `npm ci --no-audit` install step and no npm-specific build tuning flags.