feat: add Docker image metadata support

- Store metadata (.meta.json) alongside manifests with:
  - push_timestamp, last_pulled, downloads counter
  - size_bytes, os, arch, variant
  - layers list with digest and size
- Update metadata on manifest pull (increment downloads, update last_pulled)
- Extract OS/arch from config blob on push
- Extend UI API TagInfo with metadata fields
- Add public_url config option for pull commands
- Add Docker upstream proxy with auth support
- Add raw repository support
- Bump version to 0.2.12

nora-registry/src/secrets/env.rs

@@ -101,7 +101,9 @@ mod tests {
     #[tokio::test]
     async fn test_get_secret_optional_not_found() {
         let provider = EnvProvider::new();
-        let secret = provider.get_secret_optional("NONEXISTENT_OPTIONAL_XYZ").await;
+        let secret = provider
+            .get_secret_optional("NONEXISTENT_OPTIONAL_XYZ")
+            .await;
         assert!(secret.is_none());
     }