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/index/Events.vue

@@ -5,11 +5,14 @@
       <div class="max-w-6xl mx-auto px-4">
         <h3 class="text-2xl font-bold text-gray-900 mb-6">校友活动</h3>
         <div class="grid md:grid-cols-3 gap-6">
-          <div v-for="event in events" :key="event.id" class="bg-white shadow rounded-xl p-6">
-            <h4 class="font-semibold text-lg mb-2">{{ event.title }}</h4>
-            <p class="text-sm text-gray-600 mb-1">日期：{{ useChineseDateFormat(event.date) }}</p>
-            <p class="text-sm text-gray-600 mb-4">地点：{{ event.location }}</p>
-            <a :href="event.path" class="bg-secondary text-white px-5 py-2 rounded-lg hover:opacity-90">阅读详情</a>
+          <div v-for="event in events" :key="event.id" class="bg-white shadow rounded-xl">
+            <img :src="event.cover" :alt="event.title" class="rounded-xl" />
+            <div class="p-6">
+              <h4 class="font-semibold text-lg mb-2">{{ event.title }}</h4>
+              <p class="text-sm text-gray-600 mb-1">日期：{{ useChineseDateFormat(event.date) }}</p>
+              <p class="text-sm text-gray-600 mb-4">地点：{{ event.location }}</p>
+              <a :href="event.path" class="bg-secondary text-white px-5 py-2 rounded-lg hover:opacity-90">阅读详情</a>
+            </div>
           </div>
         </div>
       </div>