Surface pending private Paykit preference updates to users

[ovitrif]

Android equivalent of synonymdev/bitkit-ios#582, fixed on iOS by synonymdev/bitkit-ios#583.

Found during a retroactive post-merge review of #941 and #945.

Problem

The Android private contact payment preference can diverge from the actual published private Paykit endpoint state without user-visible feedback.

Current master references:

• PaymentPreferenceViewModel.setPrivateContactsEnabled() updates sharesPrivatePaykitEndpoints before the private enable/disable operation has fully confirmed the desired endpoint state: https://github.com/synonymdev/bitkit-android/blob/master/app/src/main/java/to/bitkit/ui/settings/paymentPreference/PaymentPreferenceViewModel.kt#L78-L105
• PrivatePaykitRepo.disableSharingAndPruneUnsavedContactState() marks cleanupPending internally when endpoint tombstoning fails, but still returns success to callers: https://github.com/synonymdev/bitkit-android/blob/master/app/src/main/java/to/bitkit/repositories/PrivatePaykitRepo.kt#L263-L280
• PayContactsViewModel.disableContactPayments() and SettingsViewModel.removePaykitEndpoints() depend on that result, so they may proceed as if private cleanup completed while remote cleanup is still pending: https://github.com/synonymdev/bitkit-android/blob/master/app/src/main/java/to/bitkit/ui/screens/profile/PayContactsViewModel.kt#L125-L175 and https://github.com/synonymdev/bitkit-android/blob/master/app/src/main/java/to/bitkit/viewmodels/SettingsViewModel.kt#L210-L228

Expected follow-up

Match the iOS behavior from synonymdev/bitkit-ios#583:

• private sharing/payment preference UI should only reflect the new steady state after endpoint publication/removal is confirmed, or
• if publication/removal is deferred or fails, keep/restore the previous user-visible state and surface an error or pending state instead of implying the preference was applied.

For the disable path specifically, avoid showing private contact payments as disabled/cleaned up if private endpoint tombstoning is only pending.