Add 'Today' as a filter option on the admin dashboard

As an admin, I want to filter dashboard metrics by "Today" so I can view accurate real-time data and make quicker decisions.

<img width="1591" height="725" alt="Image" src="https://github.com/user-attachments/assets/31315b19-357b-4b3d-be20-46712f714b44" />
