fix(ssh): display SSH login logs in server timezone

[wanghe-fit2cloud]

What this PR does / why we need it?

Refs #13860. The SSH login log page formatted the date with the browser timezone, so when the client timezone differs from the server (e.g. server Asia/Taipei, browser Europe/Berlin) the displayed time was shifted by the offset while auth.log, the terminal and the CSV export all show server time.

Summary of your change

• add dateFormatServerTimezone, which formats the timestamp using its own offset instead of converting it to the browser timezone
• use it for the date column of the SSH login log page

The CSV export (agent/utils/csv_export/ssh_log.go) already formats Date with the location parsed from the log, so the page and the export are now consistent.

Please indicate you've done the following:

• Made sure tests are passing and test coverage is added if needed.
• Made sure commit message follow the rule of Conventional Commits specification.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed.