New 'TODAY' button in the window picker shows birds since a
configurable start hour (default 6 AM). The window grows through
the day and resets each morning.
Start hour is adjustable in the settings panel ('Today starts at'
slider) and persists in localStorage (bird:todayStart).
Co-Authored-By: Claude Opus 4 <noreply@anthropic.com>
Chris Sader
896901f799
