Fix SSE route dependency and align architecture docs

backend/app/schemas/__init__.py

@@ -1,3 +1,5 @@
+"""Initialize the app.schemas package."""
+
 from .doc import (
     DocumentUploadResponse,
     DocumentInfo,
@@ -24,6 +26,8 @@ from .compliance import (
     ComplianceChatRequest,
     AnalyzeResponse,
 )
+# Keep package boundaries explicit so backend imports stay predictable.
+
 
 __all__ = [
     "DocumentUploadResponse",