Fix: sync mail login with OAuth authorization on load (glpi 10)

[Rom1-B]

Checklist before requesting a review

Please delete options that are not relevant.

• I have performed a self-review of my code.
• I have added tests (when available) that prove my fix is effective or that my feature works.
• I have updated the CHANGELOG with a short functional description of the fix or new feature.
• This change requires a documentation update.

Description

• It fixes !46573
• The mail collector login field for an OAuth IMAP connection is hidden and auto-filled from the selected OAuth authorization.
• It was only refreshed when the user manually changed the authorization dropdown, never when the dropdown resolved its value on initial form load.
• This left the login field empty in some cases, causing a misleading "cannot login, user or password wrong" error.
• The login field is now also synced right after the authorization dropdown finishes loading.
• No automated test was added: this repository has no PHPUnit or E2E test infrastructure, and the fix lives entirely in inline JS, so it was instead validated manually against a live GLPI instance.

Screenshots (if appropriate):