When tapping Back from ScanView, BusinessListView remounts and .task fires
loadBusinesses() which sees AppPrefs.lastBusinessId still set — immediately
re-navigating into the same business. Fix: clear lastBusinessId on back,
and add skipAutoNav flag to also prevent single-business auto-select from
firing when user explicitly navigated back.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>