Adds a centralized BackendReachability singleton fed by a Dio
interceptor (connection-level failures only) and connectivity_plus.
PolledValue subscribes to it and pauses on offline / reloads
immediately on reconnect, replacing the previous per-card error
cascade. MainShell renders a global OfflineBanner with Retry and
Settings actions; cards downgrade error→stale when offline so the
banner is the only red element.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
PolledValue gains pause()/resume() methods. ScannersStatusCard and
NotificationsList now implement RouteAware (didPushNext/didPopNext)
and WidgetsBindingObserver to stop API calls and tick timers when
the widget is not visible, resuming with an immediate fetch on return.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
The four polling status cards (ARP, mDNS, scanners summary, devices
summary) each rolled their own Timer/_status/_error/_isLoading state and
flipped to a red 'Error' UI on the first failed poll, throwing away
last-known-good data that was still in memory. A momentary backend blip
made every card flash red.
Introduce PolledValue<T>, a ChangeNotifier that owns the periodic timer,
in-flight CancelToken, last value, last error, and a freshness
classification (initialLoading / fresh / stale / error). 'stale' kicks in
on the first failure but keeps the value visible; 'error' only takes over
after staleErrorAfter elapses without a success (30s for the 5s scanner
polls, 3min for the 1min device-summary poll). All four cards now branch
on freshness and show a small live-updating warning icon with a tooltip
('Last updated N ago — <error>') while stale, instead of flipping red.
Also threads CancelToken? through the three polled GET endpoints.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
