Fix SSE route dependency and align architecture docs

backend/app/services/parser/__init__.py

@@ -1,6 +1,8 @@
-"""文档解析服务"""
+"""Initialize the app.services.parser package."""
 
 from .pdf_parser import PDFParser
 from .docx_parser import DocxParser
+# Keep package boundaries explicit so backend imports stay predictable.
+
 
 __all__ = ["PDFParser", "DocxParser"]