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/subject-badge.tsx

@@ -13,7 +13,7 @@ export function SubjectBadge({ shortName, tone, size = 'medium', style }: Props)
 }
 
 const styles = StyleSheet.create({
-  base: { alignItems: 'center', justifyContent: 'center', borderRadius: radius.control },
+  base: { alignItems: 'center', justifyContent: 'center', borderRadius: radius.control, borderCurve: 'continuous' },
   small: { minWidth: 32, height: 32, paddingHorizontal: 6 },
-  medium: { minWidth: 44, height: 44, paddingHorizontal: 8, borderRadius: 14 },
+  medium: { minWidth: 44, height: 44, paddingHorizontal: 8, borderRadius: 14, borderCurve: 'continuous' },
 });