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/card.tsx

@@ -19,5 +19,5 @@ export function Card({ children, tone = 'surface', padding = spacing[5], style,
 }
 
 const styles = StyleSheet.create({
-  base: { borderRadius: radius.card },
+  base: { borderRadius: radius.card, borderCurve: 'continuous' },
 });