Widget distance menu: the Distance picker only makes sense for
Cheapest ordering. It was hidden for Favourites but Closest still
showed it (regressed when the per-widget Distance picker was added).
parameterSummary now nests When clauses: Distance visible for
Cheapest only; Closest and Favourites hide it.
Notifications: three compounding defects kept real geofence alerts
from ever firing while the app was suspended:
1. Always permission was never properly requested. requestPermissions
fired WhenInUse and Always back-to-back; iOS ignores the second
call while the first prompt is pending, leaving the app stuck on
WhenInUse — and region entries are never delivered in the
background. Added locationManagerDidChangeAuthorization to
ProximityMonitor: escalate WhenInUse -> Always, and re-register
geofences on grant (regions registered under WhenInUse-only won't
deliver in the background).
2. The 18-region window was frozen in the background. Re-registration
lived in SwiftUI .onChange(of: locationManager.current), which
never runs while suspended. Added a delegate hook
(LocationManager.onLocationUpdate) fired from didUpdateLocations on
every fix including background significant-change wake-ups; the app
wires it to re-register geofences around the new position.
3. Region-registration failures were invisible. monitoringDidFailFor
was never implemented, so a failed startMonitoring (region budget,
auth, radius) silently stopped alerts. Now surfaced as
monitor.lastRegionError and shown in Settings -> Debug; cleared on
the next successful registration.