test(activity): fix flaky test by generating fresh events for today group

- Resolves timezone and day boundary issues by creating fresh "today" events in the test case.

frontend/tests/components/activity/ActivityFeed.test.tsx

@@ -386,10 +386,24 @@ describe('ActivityFeed', () => {
     });
 
     it('shows event count in group header', () => {
-      render(<ActivityFeed {...defaultProps} />);
+      // Create fresh "today" events to avoid timezone/day boundary issues
+      const todayEvents: ProjectEvent[] = [
+        createMockEvent({
+          id: 'today-event-1',
+          type: EventType.APPROVAL_REQUESTED,
+          timestamp: new Date().toISOString(),
+        }),
+        createMockEvent({
+          id: 'today-event-2',
+          type: EventType.AGENT_MESSAGE,
+          timestamp: new Date().toISOString(),
+        }),
+      ];
+
+      render(<ActivityFeed {...defaultProps} events={todayEvents} />);
 
       const todayGroup = screen.getByTestId('event-group-today');
-      // Today has 2 events in our mock data
+      // Today has 2 events
       expect(within(todayGroup).getByText('2')).toBeInTheDocument();
     });
   });