feat(core): implement Git repository operations with gRPC services

- Add advertise_refs functionality for Git protocol communication
- Implement archive service with TAR/ZIP format support and streaming
- Create blame service for Git file annotation with line tracking
- Add branch management including create, delete, rename and compare operations
- Implement merge checking with conflict detection and fast-forward handling
- Add cherry-pick functionality for applying commits between branches
- Integrate gix library for Git repository operations and object handling
- Add comprehensive test suite covering all Git operations
- Implement proper error handling and repository validation
- Add pagination support for large result sets
- Create protobuf definitions for all Git operations and data structures
- Add build system for gRPC code generation and dependency management

refs/list_refs.rs

@@ -0,0 +1,25 @@
+use crate::bare::GitBare;
+use crate::error::GitResult;
+use crate::pb::ReferenceAdvertisement;
+
+impl GitBare {
+    pub fn list_refs(&self) -> GitResult<Vec<ReferenceAdvertisement>> {
+        let repo = self.gix_repo()?;
+        let mut refs = Vec::new();
+        for r in repo.references()?.all()? {
+            let mut r = match r {
+                Ok(r) => r,
+                Err(_) => continue,
+            };
+            let hex = r.peel_to_id().map(|id| id.to_string()).unwrap_or_default();
+            refs.push(ReferenceAdvertisement {
+                name: r.name().to_string(),
+                target_oid: Some(self.oid_to_pb(hex)),
+                peeled_oid: None,
+                symbolic: r.target().try_id().is_none(),
+                symbolic_target: String::new(),
+            });
+        }
+        Ok(refs)
+    }
+}