Feat: Add gRPC support

[ichbingautam]

gRPC Support

Protocol Buffers: Defined service contract in
proto/cache.proto

• Dual Protocol: The server now listens on both HTTP (:8080) and gRPC (:50051) simultaneously.
• gRPC Adapter: Implemented a seamless adapter layer that maps gRPC requests to the core raft-consensus service logic.
• Backward Compatibility
  • Existing HTTP endpoints (/get, /set, /join) continue to function without changes.
  • Data written via HTTP is readable via gRPC and vice versa.

##Usage
Start the server (gRPC listens on default port :50051):

./server -node_id node1 -bootstrap

Run integration verification:

go run scripts/verify_compatibility.go