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

tag/verify_tag.rs

@@ -0,0 +1,35 @@
+use crate::bare::GitBare;
+use crate::error::GitResult;
+use crate::pb::{VerifiedSignature, VerifyTagRequest};
+
+impl GitBare {
+    pub fn verify_tag(&self, request: VerifyTagRequest) -> GitResult<VerifiedSignature> {
+        let result = duct::cmd(
+            "git",
+            [
+                "--git-dir",
+                self.bare_dir.to_string_lossy().as_ref(),
+                "tag",
+                "-v",
+                &request.name,
+            ],
+        )
+        .stdout_capture()
+        .stderr_capture()
+        .unchecked()
+        .run()?;
+        let verified = result.status.success();
+        Ok(VerifiedSignature {
+            verified,
+            reason: if verified {
+                crate::pb::verified_signature::Reason::Valid as i32
+            } else {
+                crate::pb::verified_signature::Reason::GpgverifyError as i32
+            },
+            signature: String::new(),
+            payload: String::new(),
+            key_fingerprint: String::new(),
+            signer: String::new(),
+        })
+    }
+}