feat(stats): implement SleepTimetable with enhanced date formatting and fixed tests

frontend/src/components/stats/SleepTimetable.tsx

@@ -9,15 +9,16 @@ interface TimetableProps {
   day_end: string;
 }
 
-function getDayName(dateStr: string) {
+export function getDayName(dateStr: string) {
   return new Date(dateStr + 'T00:00:00').toLocaleDateString('en-US', { weekday: 'short' });
 }
 
-function formatDayLabel(dateStr: string) {
+export function formatDayLabel(dateStr: string) {
   const date = new Date(dateStr + 'T00:00:00');
   const weekday = date.toLocaleDateString('en-US', { weekday: 'short' });
   const day = date.getDate();
-  return `${weekday} ${day}`;
+  const month = date.getMonth() + 1;
+  return `${weekday} ${day}/${month}`;
 }
 
 function formatTimeLabel(mins: number) {
@@ -176,7 +177,7 @@ const Timetable = ({ from_date, to_date, day_start, day_end }: TimetableProps) =
           <div className="h-2" /> {/* Empty corner cell */}
           {visibleDays.map((day) => (
             <div key={day} className="text-center text-[10px] font-medium text-gray-500 uppercase flex items-center justify-center h-2">
-              {getDayName(day)}
+              {formatDayLabel(day)}
             </div>
           ))}
         </div>

frontend/src/components/stats/__tests__/SleepTimetableUtils.test.ts

@@ -0,0 +1,9 @@
+import { describe, it, expect } from 'vitest';
+import { formatDayLabel } from '../SleepTimetable';
+
+describe('formatDayLabel', () => {
+  it('formats date as "Weekday D/M"', () => {
+expect(formatDayLabel('2025-06-09')).toBe('Mon 9/6');
+expect(formatDayLabel('2025-06-10')).toBe('Tue 10/6');
+    });
+});