When Simkl refuses to link an account, Link Simkl now shows Simkl's
reason instead of "Request failed with status code 400", and the server log
records it. If a proxy between Foreseerr and Simkl refuses the request, the
text of its error page is shown instead.
Saving a Simkl Client ID in Settings → Integrations now checks the ID
with Simkl. A wrong Client ID is rejected with Simkl's reason; before, any
value was accepted. The Simkl health check logs why it failed.