chore: delete empty app/routes directory

The legacy route files were migrated to modules. The directory only
contained an empty __init__.py. Updated docs to reflect new location.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/architecture/request-flow.md

@@ -226,9 +226,9 @@ async def get_shop_products(request: Request):
 **Example Handler**:
 
 ```python
-from app.routes import shop_pages
+# Routes are defined in modules: app/modules/<module>/routes/pages/storefront.py
 
-@router.get("/shop/products")
+@router.get("/products")
 async def shop_products_page(
     request: Request,
     db: Session = Depends(get_db)