[Enhancement] Add logout confirmation dialog

[niat-web]

##Feature Request

Current behavior:
When user clicks the "Logout" button in the navbar,
they are immediately logged out with no confirmation.

Expected behavior:
Show a small confirmation dialog:
"Are you sure you want to logout?"

• "Yes, Logout" button(logs out)
• "Cancel" button (stays logged in)

Why this is important:
User might accidentally click logout
while they are in the middle of something.

Technical implementation:
Add a simple modal component in React
that appears when logout button is clicked.
Only call the logout API when user confirms.

Acceptance Criteria:

• Confirmation dialog appears on logout click
• Cancel button keeps user logged in
• Confirm button logs user out
• Dialog has clean, simple design