fix(web): timeline group date formatting (#11392)

* fix(web): timeline group date formatting

* add isValid check

* remove duplicate type

web/src/lib/utils/timeline-util.spec.ts

@@ -0,0 +1,49 @@
+import { formatGroupTitle } from '$lib/utils/timeline-util';
+import { DateTime } from 'luxon';
+
+describe('formatGroupTitle', () => {
+  beforeAll(() => {
+    vi.useFakeTimers();
+    vi.setSystemTime(new Date('2024-07-27T12:00:00Z'));
+  });
+
+  afterAll(() => {
+    vi.useRealTimers();
+  });
+
+  it('formats today', () => {
+    const date = DateTime.fromISO('2024-07-27T01:00:00Z');
+    expect(formatGroupTitle(date.setLocale('en'))).toBe('today');
+    expect(formatGroupTitle(date.setLocale('es'))).toBe('hoy');
+  });
+
+  it('formats yesterday', () => {
+    const date = DateTime.fromISO('2024-07-26T23:59:59Z');
+    expect(formatGroupTitle(date.setLocale('en'))).toBe('yesterday');
+    expect(formatGroupTitle(date.setLocale('fr'))).toBe('hier');
+  });
+
+  it('formats last week', () => {
+    const date = DateTime.fromISO('2024-07-21T00:00:00Z');
+    expect(formatGroupTitle(date.setLocale('en'))).toBe('Sunday');
+    expect(formatGroupTitle(date.setLocale('ar-SA'))).toBe('الأحد');
+  });
+
+  it('formats date 7 days ago', () => {
+    const date = DateTime.fromISO('2024-07-20T00:00:00Z');
+    expect(formatGroupTitle(date.setLocale('en'))).toBe('Sat, Jul 20');
+    expect(formatGroupTitle(date.setLocale('de'))).toBe('Sa., 20. Juli');
+  });
+
+  it('formats date this year', () => {
+    const date = DateTime.fromISO('2020-01-01T00:00:00Z');
+    expect(formatGroupTitle(date.setLocale('en'))).toBe('Wed, Jan 1, 2020');
+    expect(formatGroupTitle(date.setLocale('ja'))).toBe('2020年1月1日(水)');
+  });
+
+  it('returns "Invalid DateTime" when date is invalid', () => {
+    const date = DateTime.invalid('test');
+    expect(formatGroupTitle(date.setLocale('en'))).toBe('Invalid DateTime');
+    expect(formatGroupTitle(date.setLocale('es'))).toBe('Invalid DateTime');
+  });
+});