fix: visible Liquid Glass again, group icon on group events, week today colour

- Liquid Glass: the calendar content now scrolls underneath a translucent
  safeAreaInset bar (real glass look restored) while the inline title stays
  reliable — toggling Liquid Glass is visibly different again.
- Group events are prefixed with the group's own emoji icon (from group
  settings) instead of a generic people glyph, so they're recognisable.
- Week view: today's column header now uses the configured "today" colour
  instead of the accent colour (matches the current-time line).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Calendarr iOS/Views/Calendar/WeekView.swift

@@ -61,7 +61,7 @@ struct WeekView: View {
             ForEach(weekDays, id: \.self) { day in
                 Text(headerFmt.string(from: day).uppercased())
                     .font(.system(size: 10, weight: .semibold))
-                    .foregroundStyle(cal.isDateInToday(day) ? Color.accentColor : Color(hex: textHex).opacity(secondaryTextOpacity(textContrast)))
+                    .foregroundStyle(cal.isDateInToday(day) ? Color(hex: todayHex) : Color(hex: textHex).opacity(secondaryTextOpacity(textContrast)))
                     .frame(maxWidth: .infinity, minHeight: 36)
                     .overlay(alignment: .trailing) {
                         Rectangle().fill(Color(hex: lineHex).opacity(gridLineOpacity(lineContrast))).frame(width: 0.5)