feat: 添加可配置场景注册表与规则引擎

- 新增场景基类、配置加载、注册表与原语模块
- 添加 r10_refund_split 规则及场景 JSON Schema
- 扩展 scan 引擎与 scenarios API
- 新增场景注册表/配置/集成测试
- 更新前端 App、api、labels 支持新场景

backend/tests/test_scenario_registry.py

@@ -0,0 +1,74 @@
+"""场景插件框架测试：注册表、场景 scan() 产出、/scenarios API（纯逻辑，无需数据库）。"""
+
+from __future__ import annotations
+
+from fastapi.testclient import TestClient
+
+from app.main import app
+from app.scenarios.base import ScanOutcome
+from app.scenarios.churn_fraud import ChurnFraudScenario, CohortPoint
+from app.scenarios.registry import SCENARIO_REGISTRY, get_scenario, scenario_meta
+from app.scenarios.split_contract import ContractRecord, SplitContractScenario
+
+
+def test_registry_contains_builtin_scenarios():
+    # 导入 app.scenarios.* 已通过自动发现触发 @register_scenario 注册 R8/R9
+    assert "R8" in SCENARIO_REGISTRY
+    assert "R9" in SCENARIO_REGISTRY
+    assert get_scenario("R8") is SplitContractScenario
+    assert get_scenario("R9") is ChurnFraudScenario
+
+
+def test_scenario_meta_fields():
+    meta = {m["code"]: m for m in scenario_meta()}
+    assert meta["R8"]["label"] == "政企拆单"
+    assert meta["R8"]["risk_domain"] == "收入"
+    assert meta["R9"]["label"] == "养卡骗补"
+    assert set(meta["R8"]) == {"code", "title", "label", "risk_domain"}
+
+
+def test_split_scenario_scan_hits():
+    contracts = [ContractRecord(f"C{i}", f"CUST{i}", 850000) for i in range(8)]
+    scenario = SplitContractScenario(
+        contracts, approval_threshold=1_000_000, shared_controller=True
+    )
+    outcome = scenario.scan(None)
+    assert isinstance(outcome, ScanOutcome)
+    assert outcome.scanned_count == 8
+    assert len(outcome.drafts) == 1
+    draft = outcome.drafts[0]
+    assert draft.score >= scenario.score_threshold
+    assert draft.amount_involved > 0
+    assert draft.evidence["shared_controller"] is True
+
+
+def test_split_scenario_no_draft_when_clean():
+    contracts = [ContractRecord("C1", "A", 100000), ContractRecord("C2", "B", 3_000_000)]
+    outcome = SplitContractScenario(contracts, approval_threshold=1_000_000).scan(None)
+    assert outcome.drafts == []
+    assert outcome.scanned_count == 2
+
+
+def test_churn_scenario_scan_produces_draft():
+    curve = [CohortPoint(0, 1.0), CohortPoint(1, 0.95), CohortPoint(2, 0.1)]
+    scenario = ChurnFraudScenario(
+        retention_curve=curve,
+        commission_paid=300000,
+        active_ratio=0.05,
+        zero_usage_ratio=0.9,
+        channel_key="CH-001",
+    )
+    outcome = scenario.scan(None)
+    assert outcome.scanned_count == 3
+    assert len(outcome.drafts) == 1
+    draft = outcome.drafts[0]
+    assert draft.subjects["channel"] == "CH-001"
+    assert draft.score >= scenario.score_threshold
+
+
+def test_scenarios_api_endpoint():
+    client = TestClient(app)
+    resp = client.get("/scenarios")
+    assert resp.status_code == 200
+    codes = {item["code"] for item in resp.json()}
+    assert {"R8", "R9"} <= codes