* feat(backup): add YYYY-MM-DD_ date prefix to backup filenames
Refs #5584
* feat(backup): prefix backup filenames with date and time
* fix(backup): put host before date in backup filename
Backup filenames now read {host}_{date}{ext} (e.g. panel.example.com_2026-06-27_000000.db) instead of {date}_{host}{ext}, so files group by server first then sort chronologically within each server.
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.
Nikan Zeyaei