RedirectPathTranslatorSubscriber calls RedirectRepository::findMatchingRedirect() without handling RedirectLoopException

Problem/Motivation

RedirectPathTranslatorSubscriber calls RedirectRepository::findMatchingRedirect() without handling RedirectLoopException. When a redirect chain loops, the exception bubbles up and /router/translate-path returns a 500 instead of a translation result.

The redirect module catches this exception itself (see RedirectRequestSubscriber::onKernelRequestCheckRedirect()), so regular Drupal page requests survive a bad redirect. The decoupled endpoint doesn't, and a single bad redirect entity breaks path resolution for every path whose chain passes through it. On a decoupled site the frontend suddenly can't resolve any of those URLs.

Redirect matches source paths case-insensitively, so an editor who adds /News -> /news has created a self-referencing redirect without realizing it.

Steps to reproduce

1. Install redirect and decoupled_router.
2. Add a redirect from /Example to /example .
3. Request /router/translate-path?path=/Example, or create any redirect pointing at /example and request its source path.
4. The response is a 500, with RedirectLoopException in the log.

Proposed resolution

Catch RedirectLoopException around the findMatchingRedirect() call, log a warning the same way the redirect module does, and fall through to the route-level translator so the path resolves as if no redirect existed. The source path then returns a normal lookup result (or a 404) instead of an error. Patch attached.