feat(registry): add service discovery and health check capabilities

- Integrate tonic-health for gRPC service health monitoring
- Add etcd-based service registration with automatic keep-alive
- Implement dynamic configuration loading from etcd with fallback
- Remove external dependencies from docker-compose for simplified deployment
- Refactor service registration logic with improved lease management
- Add health service to gRPC server with serving status reporting

Cargo.lock

@@ -380,6 +380,7 @@ dependencies = [
  "tokio",
  "tokio-stream",
  "tonic",
+ "tonic-health",
  "tonic-prost",
  "tonic-prost-build",
  "tracing",
@@ -4636,6 +4637,7 @@ dependencies = [
  "futures-core",
  "pin-project-lite",
  "tokio",
+ "tokio-util",
 ]
 
 [[package]]
@@ -4714,6 +4716,19 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "tonic-health"
+version = "0.14.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fcfab99db777fba2802f0dfa861d1628d1ae916fb199d29819941f139ae85082"
+dependencies = [
+ "prost",
+ "tokio",
+ "tokio-stream",
+ "tonic",
+ "tonic-prost",
+]
+
 [[package]]
 name = "tonic-prost"
 version = "0.14.6"