[Accessibility] VoiceOver - No announcement when focusing on already-selected date in date range picker

Describe the bug When a date range is selected in the date picker, focusing on a date that is part of the selected range produces no accessibility announcement indicating that the date is already selected (VoiceOver, NVDA announces it correctly).

To Reproduce Steps to reproduce the behavior:

1. Go to https://reactdatepicker.com/#example-date-range-in-a-single-datepicker
2. Scroll down to "Date Range in a Single Datepicker" example
3. Open the date picker and select a start date and an end date to form a date range
4. Navigate to one of the selected dates using keyboard

Expected behavior When focusing on a date that is part of the selected range, VoiceOver should announce that the date is selected (e.g., "June 15 2026, selected" or similar).

Screenshots

https://github.com/user-attachments/assets/7b114e7c-b221-4906-8f7e-c427c09ae315

Desktop (please complete the following information):

• OS: macOS
• Browser: Chrome, Safari
• Screen reader: VoiceOver (NVDA reads the selected items correctly)