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.

app/layouts/default.vue

@@ -52,7 +52,9 @@
 
     <UMain>
       <Transition name="page" mode="out-in">
-        <NuxtPage />
+        <div>
+          <NuxtPage />
+        </div>
       </Transition>
     </UMain>