feat(pack): add raw advertise refs and stateless protocol support

- Add raw flag to AdvertiseRefsRequest to enable raw pkt-line output
- Implement advertise_refs_raw function that calls git upload-pack/receive-pack with --advertise-refs
- Add stateless flag to GitProtocolFeatures for HTTP smart protocol support
- Modify upload_pack and receive_pack to accept stateless parameter
- Update command construction to include --stateless-rpc flag when enabled
- Add raw_data field to AdvertiseRefsResponse for raw output
- Update pack cache key computation to include raw service differentiation
- Initialize raw field to false in all request creation calls

actor/sync.rs

@@ -163,6 +163,7 @@ fn sync_via_pack_service(
                 repository: Some(header.clone()),
                 protocol: None,
                 service: "upload-pack".to_string(),
+                raw: false,
             })
             .await
             .map_err(|e| format!("AdvertiseRefs: {e}"))?;