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/assets/css/main.css

@@ -1,4 +1,4 @@
-@import "./markdown.css";
+/* @import "./markdown.css"; */
 
 @import "tailwindcss";
 @import "@nuxt/ui";