Refactor CSS and HTML for improved styling and readability

- Updated common.scss to enhance spacing and formatting for better consistency.
- Added a new class for responsive design in common.scss.
- Modified coupon-list_new.html to include a comment for expired coupons.
- Improved text formatting in event-view.html for better readability and user experience.

kr/mypage/coupon-list_new.html

@@ -336,6 +336,7 @@
                     <div class="cost">7일 무료 체험</div>
                   </div>
                 </li>
+                <!-- [D] 만료 시 li에 coupon-expired 클래스 추가 -->
                 <li class="item coupon-expired">
                   <div class="itemTop">
                     <div class="info">