QTZPOC-20

QTZPOC-20: Implement .sientia model bundle import workflow

Introduces a new Temporal workflow and activities to import .sientia model bundles. This enables:
- Secure decryption and validation of bundles through a seven-gate process.
- Provisioning imported models in MLflow and updating the MongoDB model listing.
- Comprehensive status tracking in the public.experiment_run table with new IMPORT_SUCCESS/IMPORT_ERROR states.
- Dedicated metrics, robust error handling, and configurable settings.
- Includes updated e2e database fixtures and extensive unit/integration tests for bundle format, reader, and overall workflow.

tests/fixtures/bundle/golden_model_v3.metadata.json

@@ -0,0 +1,24 @@
+{
+  "parameters": {
+    "model_name": "fixture_model",
+    "target_variable": "SE",
+    "input_variables": "['feature_a', 'feature_b']",
+    "models_params": "{'alpha': 0.1}",
+    "nan_treatment": "drop",
+    "scaler_name": "StandardScaler",
+    "train_size": "0.8",
+    "test_size": "0.2",
+    "include_ar": "False",
+    "retrain": "False",
+    "start_date": "2026-01-01 00:00:00",
+    "end_date": "2026-08-01 00:00:00"
+  },
+  "metadata": {
+    "model_name": "fixture_model",
+    "experiment_name": "fixture_experiment",
+    "run_id": "8f14e45fceea167a5a36dedd4bea2543",
+    "model_version": "3",
+    "model_project": "fixture_project",
+    "export_timestamp": "2026-08-25T12:08:59.533441+00:00"
+  }
+}