Nine route files each loaded the live app and checked access, with
four return shapes, docstrings promising error tuples the code never
returned, and 41 dead 'if err: return err' branches. require_app()
backed by ResourceGrantService.get_app_for does it once; conceal=True
keeps the 404-for-denied answer the previews, WAF and slot routes
already gave, so no route's status changes. Nine query sites leave the
API layer.
