feat(admin): add initial admin dashboard structure

This commit introduces the foundational structure for the new admin dashboard.

- Utilizes @nuxt/ui to build the dashboard layout, including a collapsible sidebar and navigation.
- Adds initial pages for the dashboard, news, events, and hall of fame management.
- Implements a composable `useDashboardSidebarLinks` for managing sidebar navigation.
- Refactors the default layout by integrating the header and footer directly.
- Swaps the primary and secondary theme colors across the application.

app/pages/admin/contents/events/index.vue

@@ -0,0 +1,27 @@
+<template>
+  <UDashboardPanel>
+    <template #header>
+      <UDashboardNavbar :title="pageTitle" toggle>
+        <template #leading>
+          <UDashboardSidebarCollapse />
+        </template>
+      </UDashboardNavbar>
+    </template>
+    <template #body>
+      This is events page
+    </template>
+  </UDashboardPanel>
+</template>
+
+<script lang="ts" setup>
+const pageTitle = "活动列表"
+definePageMeta({
+  layout: "admin-dashboard",
+  title: pageTitle
+})
+useHead({
+  title: pageTitle
+})
+</script>
+
+<style></style>