refactor(actor): implement Raft consensus algorithm for cluster leader election

- Add voting mechanism with term tracking and vote persistence
- Implement election triggering logic with majority vote counting
- Add primary/replica role transition handling with state management
- Integrate health check failure detection for automatic elections
- Refactor actor messaging system for distributed coordination
- Update repository registration to query cluster for existing primary
- Add broadcast mechanism for role change notifications
- Implement proper term comparison and duplicate request filtering
- Upgrade dependency versions including tokio-util for async utilities
- Optimize code formatting and line wrapping for improved readability
- Remove redundant blank lines and improve code structure consistency
- Enhance error logging and trace information for debugging purposes

actor/message.rs

@@ -149,6 +149,9 @@ pub enum GitNodeMessage {
 
     /// A role change has occurred in the cluster.
     RoleChanged(RoleChangedEvent),
+
+    /// Health checker detected primary failure, trigger election.
+    TriggerElection,
 }
 
 #[derive(ractor_cluster::RactorMessage)]
@@ -156,7 +159,6 @@ pub enum RepoActorMessage {
     UpdateMetadata(RepositoryHeader),
 }
 
-
 /// Request for a node to vote in a PRIMARY election.
 #[derive(Debug, Clone)]
 pub struct ElectionRequest {