Keep customer time zones during account support

When an administrator opens a customer account, Miracle keeps the customer’s saved time zone. Returning to the window and repeated background checks no longer ask the administrator to replace it with the device time zone.

Support sessions also stop sending device time-zone hints or creating automatic time-zone settings for customers. The server ignores those hints from older clients during support sessions. Existing saved time zones are unchanged.

Deliberate time-zone changes in Settings still require confirmation. Added tests for repeated checks, read-only and editable support, account switches, and customers without a saved time zone.