feat(cluster): implement distributed clustering with etcd coordination

- Integrate etcd-client for distributed coordination and leader election
- Add remote client macros with proper formatting for all services
- Implement RequestMetrics for tracking RPC performance and errors
- Add rate limiting mechanism across all service endpoints
- Create ElectionRequest and ElectionResult message types for leader election
- Add role management with primary/replica switching capabilities
- Implement health checker with automatic failover detection
- Add repository count metrics for cluster monitoring
- Update Cargo.toml with etcd-client and dashmap dependencies
- Modify RepoEntry to include read_only flag for replica handling
- Implement should_accept_election logic to prevent duplicate elections
- Add RoleChangedEvent handling for cluster role updates

proto/repository.proto

@@ -139,6 +139,113 @@ message RepositoryMaintenanceResponse {
   string stderr = 3;
 }
 
+// ── Hooks Management ──────────────────────────────────────────────────
+
+message ListHooksRequest {
+  RepositoryHeader repository = 1;
+}
+
+message HookInfo {
+  string hook_type = 1;
+  string level = 2; // "server" or "custom"
+  string path = 3;
+}
+
+message ListHooksResponse {
+  repeated HookInfo hooks = 1;
+}
+
+message SetCustomHookRequest {
+  RepositoryHeader repository = 1;
+  string hook_name = 2; // "pre-receive", "update", "post-receive"
+  string content = 3;  // Hook script content
+}
+
+message RemoveCustomHookRequest {
+  RepositoryHeader repository = 1;
+  string hook_name = 2;
+}
+
+// ── Snapshot ──────────────────────────────────────────────────────────
+
+enum SnapshotStorage {
+  SNAPSHOT_STORAGE_LOCAL = 0;
+  SNAPSHOT_STORAGE_S3 = 1;
+  SNAPSHOT_STORAGE_GCS = 2;
+}
+
+message SnapshotInfo {
+  string snapshot_id = 1;
+  string relative_path = 2;
+  uint64 size_bytes = 3;
+  string created_at = 4; // ISO 8601
+  string head_oid = 5;
+}
+
+message CreateSnapshotRequest {
+  RepositoryHeader repository = 1;
+  SnapshotStorage storage = 2;
+  string storage_path = 3;
+}
+
+message CreateSnapshotResponse {
+  string snapshot_id = 1;
+  uint64 size_bytes = 2;
+  string head_oid = 3;
+}
+
+message RestoreSnapshotRequest {
+  RepositoryHeader target_repository = 1;
+  string snapshot_id = 2;
+  SnapshotStorage storage = 3;
+  string storage_path = 4;
+}
+
+message ListSnapshotsRequest {
+  RepositoryHeader repository = 1;
+  uint32 limit = 2;
+}
+
+message ListSnapshotsResponse {
+  repeated SnapshotInfo snapshots = 1;
+}
+
+message DeleteSnapshotRequest {
+  string snapshot_id = 1;
+  SnapshotStorage storage = 2;
+}
+
+// ── Repository Move ──────────────────────────────────────────────────
+
+enum MoveRepositoryState {
+  MOVE_STATE_UNKNOWN = 0;
+  MOVE_STATE_PREPARING = 1;
+  MOVE_STATE_TRANSFERRING = 2;
+  MOVE_STATE_VERIFYING = 3;
+  MOVE_STATE_COMPLETED = 4;
+  MOVE_STATE_FAILED = 5;
+  MOVE_STATE_CANCELLED = 6;
+}
+
+message MoveRepositoryRequest {
+  RepositoryHeader source_repository = 1;
+  RepositoryHeader target_repository = 2;
+}
+
+message MoveRepositoryResponse {
+  MoveRepositoryState state = 1;
+  string error_message = 2;
+}
+
+message FetchRepositoryDataRequest {
+  RepositoryHeader repository = 1;
+}
+
+message FetchRepositoryDataResponse {
+  bytes data = 1;
+  bool done = 2;
+}
+
 service RepositoryService {
   rpc GetRepository(GetRepositoryRequest) returns (Repository);
   rpc InitRepository(InitRepositoryRequest) returns (Repository);
@@ -154,4 +261,19 @@ service RepositoryService {
   rpc GarbageCollect(GarbageCollectRequest) returns (RepositoryMaintenanceResponse);
   rpc Repack(RepackRequest) returns (RepositoryMaintenanceResponse);
   rpc WriteCommitGraph(WriteCommitGraphRequest) returns (RepositoryMaintenanceResponse);
+
+  // Hooks management
+  rpc ListHooks(ListHooksRequest) returns (ListHooksResponse);
+  rpc SetCustomHook(SetCustomHookRequest) returns (google.protobuf.Empty);
+  rpc RemoveCustomHook(RemoveCustomHookRequest) returns (google.protobuf.Empty);
+
+  // Snapshot operations
+  rpc CreateSnapshot(CreateSnapshotRequest) returns (CreateSnapshotResponse);
+  rpc RestoreSnapshot(RestoreSnapshotRequest) returns (google.protobuf.Empty);
+  rpc ListSnapshots(ListSnapshotsRequest) returns (ListSnapshotsResponse);
+  rpc DeleteSnapshot(DeleteSnapshotRequest) returns (google.protobuf.Empty);
+
+  // Repository move
+  rpc MoveRepository(MoveRepositoryRequest) returns (MoveRepositoryResponse);
+  rpc FetchRepositoryData(FetchRepositoryDataRequest) returns (stream FetchRepositoryDataResponse);
 }