updateLastReadMessageIfNewer
abstract suspend fun updateLastReadMessageIfNewer(contact: String, messageUuid: Long, lastReadTimestamp: Long): Int(source)
Conditional UPDATE that only writes newer timestamps. Callers must ensure the contact-settings row exists (e.g. via insertContactSettingsIgnore) before calling this inside the same transaction.
Returns the affected row count (1 = updated, 0 = no-op) for testability; callers outside tests typically ignore it.