Builds on rc4 (bedtime schedule fix, #113) and adds resilience against Google's transient API errors.
Transient error resilience (#117, thanks to @Naumsede): Google's Family Link API regularly returns transient 503/500 errors,
especially on appsandusage, which previously dropped every sensor to unavailable even though the data was unchanged. The
integration now keeps the last successful fetch in memory and serves it during transient errors, with per-endpoint fallbacks.
Re-authentication still works as before, and the cache clears on restart.
Also included from rc4 (bedtime schedule fix, #113): the bedtime and school time schedules are now actually parsed from the API and
the override uses your real configured hours for the current day instead of a hardcoded default.
Feedback welcome before this is promoted to a stable release.