Fix Docker push/pull: add PATCH endpoint for chunked uploads

- Add PATCH handler for /v2/{name}/blobs/uploads/{uuid} to support
  chunked blob uploads (Docker sends data chunks via PATCH)
- Include Range header in PATCH response to indicate bytes received
- Add Docker-Content-Digest header to GET manifest responses
- Store manifests by both tag and digest for proper pull support
- Add parking_lot dependency for upload session state management

Cargo.lock

@@ -1212,6 +1212,7 @@ dependencies = [
  "httpdate",
  "indicatif",
  "lazy_static",
+ "parking_lot",
  "prometheus",
  "reqwest",
  "serde",