Review follow-up. spanFirstDay/spanLastDay resolved every event in the
device zone, but all-day events live at UTC midnights with an exclusive
end — east of UTC (e.g. Europe/Berlin) that pushed spanLastDay onto the
next day, so a single-day all-day event reported spansMultipleDays and
leaked onto a second agenda day. Resolve all-day dates in UTC, matching
the Week view and detail card. Adds eastern-zone regression tests that
the prior UTC-only tests could not catch.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Jean-Luc Makiola
3ec46c8631