fix: day grouping compares against the local date, not the UTC one

renderFiles() derived "today" from new Date().toISOString(), which is
UTC, and compared it to f.date — the recording start in local time,
parsed server-side out of the filename. In any non-UTC timezone the two
disagree for part of every day, and the current day's group (the one
always wanted open) renders collapsed: 00:00-02:00 local in UTC+2, most
of the evening in UTC-5.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

webui.html

@@ -772,7 +772,11 @@ function renderFiles(files) {
   document.getElementById('empty').style.display = visible ? 'none' : '';
 
   const days = groupByDay(files);
-  const today = new Date().toISOString().slice(0, 10);
+  // Local date, not toISOString() — f.date is the recording start in local
+  // time, so a UTC "today" leaves the current day collapsed for part of every
+  // day in any non-UTC timezone (00:00–02:00 in UTC+2, all evening in UTC−5).
+  const now = new Date();
+  const today = `${now.getFullYear()}-${pad(now.getMonth() + 1)}-${pad(now.getDate())}`;
 
   days.forEach((dayFiles, day) => {
     const dayId = 'day-' + day.replace(/-/g, '');