feat: redesign day picker with expandable calendar, status markers & Playwright E2E testing

- Replace modal calendar with inline expandable calendar widget integrated into the day picker.
- Add status indicator dots (attended/absent/pending) to month calendar grid matching day picker.
- Disable and gray out weekend days in calendar when weekend schedule is turned off.
- Redesign extend bar with integrated handle that aligns with the palette.
- Remove start-to-end timing on Today screen's class time rail, showing only start time.
- Implement Playwright E2E and visual testing suite with multi-screen capture scripts.
- Add cascade DELETE endpoints for subjects and versioned recurring timetable entries.

components/ui/bottom-sheet.tsx

@@ -39,7 +39,7 @@ const styles = StyleSheet.create({
   overlay: { flex: 1, justifyContent: 'flex-end', backgroundColor: colors.neutral.scrim },
   backdrop: { ...StyleSheet.absoluteFillObject },
   keyboard: { width: '100%', maxHeight: '92%' },
-  sheet: { borderTopLeftRadius: radius.sheet, borderTopRightRadius: radius.sheet, backgroundColor: colors.neutral.surface, paddingHorizontal: spacing[6], paddingTop: spacing[3], ...shadow.floating },
+  sheet: { borderTopLeftRadius: radius.sheet, borderTopRightRadius: radius.sheet, borderCurve: 'continuous', backgroundColor: colors.neutral.surface, paddingHorizontal: spacing[6], paddingTop: spacing[3], ...shadow.floating },
   handle: { width: 36, height: 4, alignSelf: 'center', borderRadius: radius.pill, backgroundColor: colors.neutral.border },
   header: { minHeight: 60, flexDirection: 'row', alignItems: 'center', justifyContent: 'space-between', gap: spacing[4] },
   body: { paddingBottom: spacing[5] },