fix(code-quality): Fix for Explicit returns mixed with implicit (fall through) returns

[jackseceng]

General fix: ensure redirect_url has an explicit return for all code paths, and avoid return None after abort() in view functions. In Flask handlers, either return a valid response object/string/tuple or raise via abort().

Best fix in this file: in app/app.py, inside redirect_url (around lines 167–201), replace the abort(...); return None block with a direct return page_not_found(...) using the existing error handler function. This guarantees an explicit Flask response object on that branch and removes the problematic None return path. Also add a final defensive return after the match to ensure an explicit response in all analyzer-visible paths.

Suggested fixes powered by Copilot Autofix. Review carefully before merging.