Fix SSE route dependency and align architecture docs

backend/app/services/storage/__init__.py

@@ -1,6 +1,18 @@
-"""存储服务"""
+"""Initialize the app.services.storage package."""
+# Keep package boundaries explicit so backend imports stay predictable.
 
-from .milvus_client import MilvusClient
-from .minio_client import MinIOClient
 
 __all__ = ["MilvusClient", "MinIOClient"]
+
+
+def __getattr__(name: str):
+    """Handle getattr for this module."""
+    if name == "MilvusClient":
+        from .milvus_client import MilvusClient
+
+        return MilvusClient
+    if name == "MinIOClient":
+        from .minio_client import MinIOClient
+
+        return MinIOClient
+    raise AttributeError(name)