[stable34] fix(config): mask the Euro-Office jwt_secret as sensitive - #63332

Both sensitive-key allowlists carried an `onlyoffice` entry but nothing
for `eurooffice`, so the document server signing key was printed in
full while the ONLYOFFICE one next to it was redacted.

SystemConfig covers `occ config:list system`, which is where the key
lands when the app is configured through config.php. AppConfig covers
plain `occ config:list` and the admin support report, which is where it
lands when it is set through the app's own settings page.

Fixes: #63302

Assisted-by: ClaudeCode:claude-opus-5
Signed-off-by: Christoph Schaefer <christoph.schaefer@nextcloud.com>