refactor(api): TOML 配置 SSOT、统一错误契约、Auth/事务加固与可观测性 (#33)

配置 SSOT（TOML + .env）
统一错误契约
Auth 与事务边界
Redis / Celery 可靠性:业务 Redis（DB/0）与 Celery broker/backend（DB/1）显式拆分；连接池、sync client
可观测性（OpenTelemetry + LGTM）

api/tests/evaluation/test_memoir_pipeline_run_router.py

@@ -1,6 +1,7 @@
 """GET /users/{user_id}/memoir-pipeline-run（快照读取）。"""
 
 import pytest
+from tests.conftest import install_test_error_handlers
 from httpx import ASGITransport, AsyncClient
 
 from app.features.evaluation.internal_auth import get_internal_eval_principal
@@ -42,7 +43,7 @@ async def test_memoir_pipeline_run_ok_by_phase1_task(
         _fake_eval,
     )
 
-    app = FastAPI()
+    app = install_test_error_handlers(FastAPI())
     app.include_router(router, prefix="/internal/api/evaluation")
 
     async def _override_auth():
@@ -78,7 +79,7 @@ async def test_memoir_pipeline_run_400_both_ids(
     )
     from app.features.evaluation.router import router
 
-    app = FastAPI()
+    app = install_test_error_handlers(FastAPI())
     app.include_router(router, prefix="/internal/api/evaluation")
 
     async def _override_auth():