fix(config): system_config_service 运行时读取 SessionLocal 修复后台配置接口500 #2246

模块 import 时 session.SessionLocal 还是 None，initialize_database 之后才赋值；
原写法在 import 时绑定到旧 None，导致 GET /api/v1/admin/ditto-emotion/config
抛 RuntimeError(数据库会话工厂未初始化) 返回 500。

改为 import 模块、运行时读取 session.SessionLocal，并补 2 个回归用例
（启动顺序绑定 / 无工厂抛错），test_system_config 29 passed。

packages/application/system_config_service.py

@@ -12,7 +12,7 @@ import logging
 import threading
 from typing import Any
 
-from packages.adapters.sqlalchemy_impl.session import SessionLocal
+from packages.adapters.sqlalchemy_impl import session as db_session
 from packages.adapters.sqlalchemy_impl.system_setting_repository import (
     SQLAlchemySystemSettingRepository,
 )
@@ -35,7 +35,9 @@ class SystemConfigService:
 
     # ── 会话 ─────────────────────────────────────────────────────
     def _get_session_factory(self):
-        factory = self._session_factory or SessionLocal
+        # 必须运行时读取模块属性：模块导入时 SessionLocal 还是 None，
+        # initialize_database() 之后才被赋值，import 时绑定会拿到旧值。
+        factory = self._session_factory or db_session.SessionLocal
         if factory is None:
             raise RuntimeError("数据库会话工厂未初始化")
         return factory

tests/unit/test_system_config.py

@@ -91,6 +91,37 @@ class TestConfigService:
     def test_default_when_missing(self, config_service):
         assert config_service.get_config("not_exist", "fallback") == "fallback"
 
+    def test_uses_module_session_factory_assigned_after_import(self):
+        # 回归：模块导入时 session.SessionLocal 为 None，initialize_database()
+        # 之后才赋值；服务必须运行时读取模块属性，而不是 import 时绑定旧值。
+        from packages.adapters.sqlalchemy_impl import session as db_session
+
+        engine = create_engine("sqlite://")
+        Base.metadata.create_all(engine)
+        factory = sessionmaker(bind=engine)
+        writer = SystemConfigService(session_factory=factory)
+        writer.set_config("late_key", 7, setting_type=SETTING_TYPE_INT)
+
+        reader = SystemConfigService()  # 不注入工厂，依赖模块级 SessionLocal
+        old = db_session.SessionLocal
+        try:
+            db_session.SessionLocal = factory
+            assert reader.get_config("late_key", 0) == 7
+        finally:
+            db_session.SessionLocal = old
+
+    def test_raises_when_no_session_factory(self):
+        from packages.adapters.sqlalchemy_impl import session as db_session
+
+        svc = SystemConfigService()
+        old = db_session.SessionLocal
+        try:
+            db_session.SessionLocal = None
+            with pytest.raises(RuntimeError):
+                svc.get_config("anything", 1)
+        finally:
+            db_session.SessionLocal = old
+
     def test_db_overrides_default(self, config_service):
         config_service.set_config("k", 20, setting_type=SETTING_TYPE_INT)
         # 再次读取应命中 DB 值，而非传入的默认