refactor(ui): adopt Nuxt UI prose styles and apply various fixes

Replaces custom `markdown.css` with the default prose styling from Nuxt UI to simplify the styling architecture. This commit also includes several other fixes and improvements:

- fix(members): Correctly
handle empty `graduateYear` strings in the member list.
- fix(layout): Wrap `NuxtPage` in a div to resolve page transition issues.
- feat(seo): Add a meta title to the homepage.
- docs(content): Correct
the title and add an image to an event page.

nuxt.config.ts

@@ -5,9 +5,9 @@ export default defineNuxtConfig({
   compatibilityDate: "2025-07-15",
   devtools: { enabled: true },
   modules: [
+    "@nuxt/ui",
     "@nuxt/content",
     "@nuxt/image",
-    "@nuxt/ui",
     "reka-ui/nuxt",
     "@nuxtjs/robots",
     "@nuxtjs/seo",