refactor: keep runtime settings below adapters

app/runtime/settings.py

@@ -0,0 +1,25 @@
+"""运行时配置读取端口，供低层适配器避免反向依赖 Application。"""
+
+from __future__ import annotations
+
+import importlib
+from collections.abc import Callable
+from typing import Any
+
+
+RuntimeSettingProvider = Callable[[str], Any]
+_provider: RuntimeSettingProvider | None = None
+
+
+def configure_runtime_setting_provider(provider: RuntimeSettingProvider) -> None:
+    """由启动组合根登记配置读取器，保持适配器只依赖 runtime 端口。"""
+    global _provider
+    _provider = provider
+
+
+def get_runtime_setting(key: str) -> Any:
+    """读取单项运行配置；启动早期未装配时回退旧 Settings ABI。"""
+    if _provider is not None:
+        return _provider(key)
+    legacy_settings = importlib.import_module("app.runtime.config").settings
+    return getattr(legacy_settings, key)