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/test_oral_normalize.py

@@ -22,27 +22,27 @@ def test_apply_rules_no_false_positive_rong() -> None:
 
 def test_normalize_respects_global_off() -> None:
     raw = "美看上我"
-    with patch("app.features.memoir.oral_normalize.settings") as m:
-        m.memoir_oral_normalize_enabled = False
-        m.memoir_oral_normalize_mode = "rules"
+    with patch("app.features.memoir.oral_normalize.memoir") as m:
+        m.oral_normalize_enabled = False
+        m.oral_normalize_mode = "rules"
         assert normalize_oral_for_memoir(raw, llm=None) == raw
 
 
 def test_normalize_rules_mode_no_llm() -> None:
     raw = "美看上我"
-    with patch("app.features.memoir.oral_normalize.settings") as m:
-        m.memoir_oral_normalize_enabled = True
-        m.memoir_oral_normalize_mode = "rules"
-        m.memoir_oral_normalize_llm_max_tokens = 512
-        m.memoir_oral_normalize_llm_max_input_chars = 8000
+    with patch("app.features.memoir.oral_normalize.memoir") as m:
+        m.oral_normalize_enabled = True
+        m.oral_normalize_mode = "rules"
+        m.oral_normalize_llm_max_tokens = 512
+        m.oral_normalize_llm_max_input_chars = 8000
         assert normalize_oral_for_memoir(raw, llm=None) == "没看上我"
 
 
 def test_normalize_mode_off_string() -> None:
     raw = "美看上我"
-    with patch("app.features.memoir.oral_normalize.settings") as m:
-        m.memoir_oral_normalize_enabled = True
-        m.memoir_oral_normalize_mode = "off"
-        m.memoir_oral_normalize_llm_max_tokens = 512
-        m.memoir_oral_normalize_llm_max_input_chars = 8000
+    with patch("app.features.memoir.oral_normalize.memoir") as m:
+        m.oral_normalize_enabled = True
+        m.oral_normalize_mode = "off"
+        m.oral_normalize_llm_max_tokens = 512
+        m.oral_normalize_llm_max_input_chars = 8000
         assert normalize_oral_for_memoir(raw, llm=None) == raw