6d46de26c4
The credential tester always reported "Authentication failed — qBittorrent rejected the credentials" for the qBittorrent service, even when credentials were correct. test_connection classified any RuntimeError whose message contained "login failed" as an auth failure — and the gateway-timeout error (502/503/504 from the reverse proxy) and the wrong-URL diagnostic both started with "qBittorrent login failed:", so a proxy timeout was reported as a credentials rejection. That sent users down the wrong path (re-entering correct passwords to fix a 504). - QbittorrentClient._login: gateway and URL/routing errors no longer contain "login failed"; only a genuine "Fails." body carries the "invalid username or password" signal. - integrations/qbittorrent.test_connection: key the auth message off "invalid username or password" specifically; all other login errors flow through translate_connection_error so the real reason (proxy timeout, wrong URL, empty body) is surfaced. After this, a failing test reports the actual cause (e.g. "qBittorrent is unreachable: reverse proxy returned HTTP 504 ...") instead of accusing the credentials. New regression test asserts a gateway error is NOT reported as "Authentication failed". 386/386 backend tests pass; ruff clean.