test: CMA自动化测试补覆盖 226→452用例, 覆盖率36%→60%

- 新增8个测试文件(bot_bridge/kpi_causality/cash/predict/reports/tax_compliance/expenses/probe_cost)
- 增强 budget/auth/users + conftest账套模式适配
- 测试驱动修复: bot_bridge导入batch_id→source_batch; cash_forecast extra空dict
- 全量: 451 passed, 1 xfailed; 报告 docs/cma-test-coverage-report.md

backend/tests/test_users.py

@@ -107,7 +107,7 @@ class TestUsers:
 
         # 验证可以用新密码登录
         login_resp = client.post("/api/cma/auth/login", json={
-            "username": "passuser", "password": "newsecret",
+            "username": "passuser", "password": "newsecret", "entity_id": 1,
         })
         assert login_resp.status_code == 200