feat(monitoring): add monitoring_service crate with Prometheus-to-gRPC bridge

Prometheus client queries training/hyperopt/GPU/K8s metrics, gRPC service
exposes unary + server-streaming RPCs, 4 unit tests, zero clippy warnings.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Cargo.lock

@@ -6144,6 +6144,32 @@ dependencies = [
  "tracing",
 ]
 
+[[package]]
+name = "monitoring_service"
+version = "1.0.0"
+dependencies = [
+ "anyhow",
+ "async-stream",
+ "axum 0.7.9",
+ "chrono",
+ "clap",
+ "common",
+ "prometheus",
+ "prost 0.14.1",
+ "prost-build",
+ "prost-types",
+ "reqwest 0.12.23",
+ "serde",
+ "serde_json",
+ "tokio",
+ "tokio-stream",
+ "tonic",
+ "tonic-prost",
+ "tonic-prost-build",
+ "tracing",
+ "tracing-subscriber",
+]
+
 [[package]]
 name = "moxcms"
 version = "0.7.6"