Panel downloads and Telegram backups were always named x-ui.db / x-ui.dump, so backups from different servers were indistinguishable. Name them after the panel address instead: the configured web domain, or the public IP (IPv4 before IPv6) when no domain is set, falling back to x-ui.
Centralized in ServerService.BackupFilename(); host is sanitized to the getDb filename charset (IPv6 colons become hyphens) and read from the mutex-guarded LastStatus to avoid racing the status goroutine.