refactor backend module architecture

tests/test_webpush_helper.py

@@ -1,4 +1,6 @@
-from app.helper.webpush import (
+import importlib
+
+from app.api.endpoints.message import (
     is_webpush_subscription_gone,
     is_wns_endpoint,
     webpush_options_for_endpoint,
@@ -41,3 +43,11 @@ def test_webpush_options_for_wns_endpoint() -> None:
 
 def test_webpush_options_for_non_wns_endpoint() -> None:
     assert webpush_options_for_endpoint("https://fcm.googleapis.com/fcm/send/abc") == {}
+
+
+def test_legacy_webpush_path_reuses_message_endpoint() -> None:
+    """旧 Web Push helper 路径应复用消息端点中的同一实现。"""
+    legacy = importlib.import_module("app.helper.webpush")
+
+    assert legacy.is_webpush_subscription_gone is is_webpush_subscription_gone
+    assert legacy.webpush_options_for_endpoint is webpush_options_for_endpoint