Enhance user verification and UI components

- Updated `auth-actions.ts` to improve user verification notification formatting and date handling.
- Modified `layout.tsx` to support dark mode styling for better user experience.
- Refactored `signup/page.tsx` to enhance layout and responsiveness.
- Introduced a new API route in `route.ts` for sending user verification notifications.
- Improved user feedback in `user-payments-table.tsx` by updating the no payment message.
- Made minor adjustments in `application-layout.tsx` for consistent padding.
- Enhanced `signup-form.tsx` to display error messages for invalid user validation.

These changes improve the user verification process, enhance UI consistency, and provide better feedback to users.

components/admin/user-payments-table.tsx

@@ -131,7 +131,7 @@ export async function UsersPaymentsTable({
     <div>
       {payments.length === 0 ? (
         <div className="h-[calc(100svh-400px)] flex flex-col items-center justify-center my-4">
-          <h3>No Users yet.</h3>
+          <h3>No user payments yet.</h3>
         </div>
       ) : (
         <>