refactor: reorganize startup persistence boundaries

tests/test_managed_resources.py

@@ -294,7 +294,7 @@ def test_startup_initializer_discovers_manifest_without_importing_resource() ->
     script = """
 import asyncio
 import sys
-from app.startup.managed_resources_initializer import (
+from app.startup.initializers.managed_resources import (
     init_managed_resources,
     stop_managed_resources,
 )
@@ -320,7 +320,7 @@ assert "pyvirtualdisplay" not in sys.modules
 
 def test_startup_shutdown_without_init_does_not_build_registry(monkeypatch) -> None:
     """未执行启动装配时，关闭入口不得通过发现声明反向初始化 Runtime。"""
-    from app.startup import managed_resources_initializer
+    from app.startup.initializers import managed_resources as managed_resources_initializer
 
     build_registry = MagicMock(side_effect=AssertionError("must not discover"))
     monkeypatch.setattr(