feat: production readiness Phase 1-2 implementation

- fix(trading_engine): replace Prometheus panic! with graceful registration
- fix(trading_service): implement partial fill matching in order book
- feat(trading_service): replace feature extraction stub with real 51-dim pipeline
- feat(trading_service): wire RiskEngine with real VaR calculator
- fix(api_gateway): implement real ML prediction proxy
- feat(data_acquisition): implement DBN data downloader
- feat(data): wire DBN uploader with MinIO integration

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

data/tests/dbn_uploader_tests.rs

@@ -229,7 +229,8 @@ async fn test_upload_generates_correct_minio_key() {
     let filename = PathBuf::from("ES.FUT_ohlcv-1m_2024-01-02.dbn");
     let prefix = "training-data/";
 
-    let key = DbnUploader::generate_upload_key(&filename, prefix);
+    let key = DbnUploader::generate_upload_key(&filename, prefix)
+        .expect("Failed to generate upload key");
 
     assert_eq!(
         key, "training-data/ES.FUT_ohlcv-1m_2024-01-02.dbn.gz",