Fix SSE route dependency and align architecture docs

backend/app/utils/__init__.py

@@ -1,4 +1,8 @@
+"""Initialize the app.utils package."""
+
 from .chunking import TextChunker, chunker
 from .logger import logger, setup_logging
+# Keep package boundaries explicit so backend imports stay predictable.
+
 
 __all__ = ["TextChunker", "chunker", "logger", "setup_logging"]