UX Improvements after migration to another instance.

[skobkin]

Is your feature request related to a problem? Please describe.

When user is moving their account to another server, they're losing access to several features that should be available to them even after migration:

• account export
• account deletion
• security settings (changing the password, TOTP, etc)

Describe the solution you'd like

• Leave the settings page and dropdown user menu as is, but make some pages unavailable

Describe alternatives you've considered

• Add more buttons with still accessible functions to this "you have moved your account" screen

Additional context

User should be able to export their data AFTER migration. They also should be able to change password in case of security breach for example.