feat(app): introduce Hall of Fame section and refactor UI

This commit adds the '名人堂' (Hall of Fame) feature and removes the Element Plus dependency.

- feat(content): Add Hall of Fame section with a new content collection, homepage component, and detail pages.
- refactor(join-us): Rewrite the 'Join Us' form to remove Element Plus, using native elements and Reka UI. The form is
temporarily disabled.
- feat(ui): Display cover images on News and Events cards.
- chore: Integrate Umami for web analytics.
- fix: Correct minor text issues, including graduation year in the footer.

app/components/AppFooter.vue

@@ -13,7 +13,7 @@
           <a href="https://tootaio.com" target="_blank" class="font-semibold hover:underline" style="color: #e24545;">
             Tootaio Studio
           </a>
-          <span class="mt-1 text-sm text-gray-400">18 级毕业学长（麦祖奕）</span>
+          <span class="mt-1 text-sm text-gray-400">2018 级毕业学长（麦祖奕）</span>
         </p>
       </div>