feat: add robots.txt and sitemap.xml routes for SEO optimization

- Implemented a new route for robots.txt to control crawler access.
- Added a sitemap.xml route to provide search engines with a list of site URLs.
- Included functions for URL normalization and XML escaping to ensure proper formatting.

components/Hero.vue

@@ -7,11 +7,22 @@
     <div class="absolute inset-0 z-0">
       <div class="absolute top-0 right-0 w-96 h-96 bg-primary-200/30 rounded-full blur-3xl" />
       <div class="absolute bottom-0 left-0 w-96 h-96 bg-gray-300/30 rounded-full blur-3xl" />
-      <!-- Hintergrundbild -->
-      <div 
-        class="absolute inset-0 opacity-10"
-        style="background-image: url('/images/club_about_us.png'); background-size: cover; background-position: center;"
-      />
+      <picture class="absolute inset-0 opacity-10">
+        <source
+          type="image/webp"
+          srcset="/images/club_about_us_hero_960.webp 960w, /images/club_about_us_hero_1600.webp 1600w"
+          sizes="(max-width: 1024px) 960px, 1600px"
+        >
+        <img
+          src="/images/club_about_us.png"
+          alt=""
+          aria-hidden="true"
+          class="w-full h-full object-cover"
+          loading="eager"
+          fetchpriority="high"
+          decoding="async"
+        >
+      </picture>
     </div>
 
     <!-- Content -->