Adds maybePrintBanner() called from three cobra hooks:
- PersistentPreRun on root: covers every subcommand invocation
- Custom HelpFunc on root: covers --help and group-level help
- Run on root: covers bare 'vaultik' with no subcommand
bannerOnce sync.Once ensures the banner prints exactly once per
process regardless of which hook(s) fire.
Removed the duplicate banner-print from fx setupGlobals; that hook
still handles the --cron/--quiet UI swap for the rest of the output.
sneak
9f537b9c4c