feat(content): add founding history page for the alumni association

This commit introduces a new page detailing the founding history of the alumni association.

- Adds the new page at `/about/founded-history` which includes the origin story, organizational structure, and a list of donors for the clubhouse.
- Restructures the `/about` route by moving the existing page to `/about/index` to accommodate nested pages.
- Updates the main navigation menu to include a dropdown link to the new 'Founding History' page.
- Adds a link to the old alumni website under 'Friendly Links' for historical reference.

app/pages/about/index.vue

@@ -0,0 +1,61 @@
+<template>
+  <UPage>
+    <UPageBody>
+      <UContainer>
+        <UPageHeader
+          title="关于校友会"
+          description="永平中学校友会成立的宗旨是连接全球校友，传承母校精神，支持在校学生成长。我们定期举办活动，推动交流与合作，并积极回馈母校。"
+        />
+
+        <UPageSection
+          title="会徽"
+          description="你了解校友会会徽的含义吗"
+          :features="logoFeatures"
+          orientation="horizontal"
+        >
+          <img class="size-88" src="/Logo.svg" alt="YPHS Alumni" />
+        </UPageSection>
+
+        <UPageSection
+          title="永平中学校歌"
+          description="这首伴随着我们整个中学生涯的曲子，想必能勾起您不少的青春回忆吧！"
+          orientation="horizontal"
+          reverse
+        >
+          <div class="flex flex-col gap-y-8">
+            <img class="w-full" src="/about/校歌.webp" alt="YPHS Alumni" />
+            <div class="flex items-center gap-x-8">
+              <p>伴奏版</p>
+              <audio
+                controls
+                class="flex-1"
+                src="/about/永平中学校歌.mp3"
+              ></audio>
+            </div>
+            <div class="flex items-center gap-x-8">
+              <p>咏唱版</p>
+              <audio
+                controls
+                class="flex-1"
+                src="/about/YongPing_SchoolSong_V2.mp3"
+              ></audio>
+            </div>
+          </div>
+        </UPageSection>
+      </UContainer>
+    </UPageBody>
+  </UPage>
+</template>
+
+<script lang="ts" setup>
+import type { PageFeatureProps } from "@nuxt/ui";
+
+const logoFeatures = ref<PageFeatureProps[]>([
+  { title: "九轮", description: "永久随时代齿轮前进" },
+  { title: "太阳九条线", description: "久久发出光芒照耀华友" },
+  { title: "三个菱形", description: "代表校友、董事会及社会人士团结一致" },
+  { title: "两道绿叶", description: "代表组织团结、不断茁壮成长" },
+]);
+</script>
+
+<style></style>