P2: Improve copy-code feedback with micro-interaction

[hasitpbhatt]

Problem: 'Copied!' flash is functional but lacks finesse. The 2s duration is too long, and there's no haptic-like micro-animation.

Fix:

• Add a brief scale bounce (1 → 1.08 → 1) on the button when copied
• Reduce duration from 2000ms to 1500ms
• Add a spring-based revert animation

Files to modify:

• js/search.js — copyCoupon() function
• css/style.css — add .deal-card-btn-code.copied animation keyframes