Simplify checkout: replace multiple card fields with one streamlined input

🔍 Problem Statement
The checkout modal shows several separate input fields for card number, expiry date, and CVV. This creates a cluttered experience for users and adds unnecessary UI complexity compared to a streamlined, single-line card field.

💡 User Story
As an end user, I want to enter my card details in one simple input field so that checkout feels faster, cleaner, and easier.

🎯 Definition of Done (DoD)
A feature is done when:

✔️ The checkout supports a single-line card field for entering card number, expiry date, and CVV.
✔️ The new card input matches modern UX standards and is consistent with other payment method fields.
✔️ The checkout UI is simplified, reducing visual clutter and improving the overall customer experience.
✔️ Existing payment functionality remains intact