Tech debt cleanup: update README, fix comments, sync shared submodule

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app.py

@@ -1,5 +1,5 @@
 from __future__ import annotations
-import path_setup  # noqa: F401  # adds shared_lib to sys.path
+import path_setup  # noqa: F401  # adds shared/ to sys.path
 from pathlib import Path
 
 from quart import g, request
@@ -23,7 +23,7 @@ async def coop_context() -> dict:
     """
     Coop app context processor.
 
-    - menu_items: direct DB query via glue layer
+    - menu_items: via shared.services.navigation
     - cart_count/cart_total: via cart service (shared DB)
     """
     from shared.infrastructure.context import base_context