feat(trading_service): compile ml_training.proto client for retrain forwarding

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

services/trading_service/build.rs

@@ -16,5 +16,18 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
             ],
             &["proto"],
         )?;
+
+    // Compile ml_training.proto (client-only, for retrain_model forwarding)
+    tonic_prost_build::configure()
+        .build_server(false)
+        .build_client(true)
+        .client_mod_attribute(".", "#[allow(unused_qualifications)]")
+        .compile_protos(
+            &["../ml_training_service/proto/ml_training.proto"],
+            &["../ml_training_service/proto"],
+        )?;
+
+    println!("cargo:rerun-if-changed=../ml_training_service/proto/ml_training.proto");
+
     Ok(())
 }

services/trading_service/src/lib.rs

@@ -50,6 +50,11 @@ pub mod proto {
     pub mod monitoring {
         tonic::include_proto!("monitoring");
     }
+
+    /// ML Training Service client definitions (for retrain forwarding)
+    pub mod ml_training {
+        tonic::include_proto!("ml_training");
+    }
 }
 
 /// Authentication interceptor with mTLS, JWT, and API key support