fix: footer links and styles

Author: mucho613

_includes/footer.html

@@ -3,7 +3,7 @@
     <img src="/img/2025/common/footer-logo.png" alt="DojoCon Japan 2025 Inspire Next." />
   </div>
   <div class="footer-social">
-    <a href="https://twitter.com/{{ site.twitter }}" target="_blank" rel="noopener" class="social-x" aria-label="X">
+    <a href="https://x.com/{{ site.twitter }}" target="_blank" rel="noopener" class="social-x" aria-label="X">
       <i class="fa-brands fa-x-twitter" style="color:#000000;"></i>
     </a>
     <a href="https://www.facebook.com/{{ site.facebook }}" target="_blank" rel="noopener" class="social-facebook" aria-label="Facebook">
@@ -16,7 +16,6 @@
   <nav class="footer-links">
     <a href="/">ホーム</a>
     <a href="/code-of-conduct">行動規範</a>
-    <a href="/sitemap">サイトマップ</a>
     <a href="/privacy">プライバシーポリシー</a>
     <a href="{{site.contact}}" target="_blank">お問い合わせ</a>
   </nav>

_sass/includes/footer.scss

@@ -14,22 +14,25 @@
   }
 
   .footer-social {
+    display: flex;
+    justify-content: center;
     margin-bottom: 24px;
+    column-gap: 28px;
 
     a {
-      display: inline-block;
-      margin: 0 14px;
       font-size: 2.2rem;
       color: #000;
-      width: 48px;
-      height: 48px;
+      width: 52px;
+      height: 52px;
       line-height: 48px;
-      border-radius: 50%;
-      background: #ffffff;
-      transition: background 0.2s, color 0.2s;
+      border-bottom: 4px solid transparent;
+      transition: border-color 0.2s;
+      display: flex;
+      align-items: center;
+      justify-content: center;
 
       &:hover {
-        background: $hover-color;
+        border-color: $hover-color;
         color: #fff;
       }
     }