feat(ai-services): complete AVM v2 ensemble — upload endpoint, per-district metrics, A/B routing

- Add POST /avm/v2/upload-training-data so AvmRetrainCronService can push
  CSV rows before triggering retraining (was called but missing)
- Add per-district MAE/MAPE/RMSE/R² to _evaluate_ensemble output;
  district_metrics are now returned in AVMv2TrainResponse and stored
  separately from global metrics in the model registry
- Add predict_with_ab() that applies the active model's ab_test_traffic_pct
  for deterministic per-property cohort assignment (v2 vs heuristic baseline)
- Add POST /avm/v2/ab-config to set traffic_pct on the active registry entry
- Add AVMv2ABConfigRequest schema
- Expand test suite: 24 → 28 tests covering upload, A/B config, and new
  validation paths; all green

Co-Authored-By: Paperclip <noreply@paperclip.ing>

libs/ai-services/tests/test_avm_v2.py

@@ -377,3 +377,68 @@ def test_compare_v1_with_v2_features():
     # v2 should capture these extra features
     assert data["v2"]["estimated_price_vnd"] > 0
     assert data["v2"]["model_version"] is not None
+
+
+# ── Upload training data ────────────────────────────────────────
+
+_CSV_HEADER = (
+    "property_type,area_m2,rooms,floor_level,total_floors,direction,floor_ratio,"
+    "building_age_years,has_elevator,has_parking,has_pool,has_legal_paper,"
+    "developer_reputation,neighborhood_score,distance_to_cbd_km,distance_to_metro_km,"
+    "distance_to_school_km,distance_to_hospital_km,distance_to_park_km,distance_to_mall_km,"
+    "flood_zone_risk,avg_price_district_3m_vnd_m2,listing_density,absorption_rate,"
+    "dom_avg,price_momentum_30d,yoy_change,renovation_score,view_quality,interior_quality,"
+    "noise_level,natural_light,month,district,price_vnd"
+)
+_CSV_ROW = (
+    "apartment,80,2,5,20,south,1.0,3,1,1,0,1,0.8,0.7,5,1,0.5,2,1,3,"
+    "0.1,85000000,10,0.3,30,0.01,0.05,0.8,0.7,0.75,0.3,0.8,3,Cầu Giấy,7000000000"
+)
+
+
+def test_upload_training_data_ok(tmp_path):
+    """Upload endpoint accepts valid CSV and returns row count."""
+    from unittest.mock import patch
+    from app import config as cfg
+    with patch.object(cfg.settings, "model_path", str(tmp_path)):
+        csv_body = f"{_CSV_HEADER}\n{_CSV_ROW}\n"
+        resp = client.post(
+            "/avm/v2/upload-training-data",
+            content=csv_body,
+            headers={"Content-Type": "text/csv"},
+        )
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["rows_received"] == 1
+
+
+def test_upload_training_data_missing_price_vnd():
+    """Upload endpoint rejects CSV without price_vnd column."""
+    bad_csv = "property_type,area_m2\napartment,80\n"
+    resp = client.post(
+        "/avm/v2/upload-training-data",
+        content=bad_csv,
+        headers={"Content-Type": "text/csv"},
+    )
+    assert resp.status_code == 400
+    assert "price_vnd" in resp.json()["detail"]
+
+
+def test_upload_training_data_empty_body():
+    """Upload endpoint rejects empty body."""
+    resp = client.post(
+        "/avm/v2/upload-training-data",
+        content=b"",
+        headers={"Content-Type": "text/csv"},
+    )
+    assert resp.status_code == 400
+
+
+# ── A/B config endpoint ─────────────────────────────────────────
+
+
+def test_ab_config_no_registry():
+    """AB config endpoint returns 404 when no model is registered (heuristic-only run)."""
+    resp = client.post("/avm/v2/ab-config", json={"traffic_pct": 0.10})
+    # Fresh test env has no registry → 404
+    assert resp.status_code == 404