site: enable Tailwind Typography so prose pages render proper headings/lists

The about page (and other pages using 'prose') rendered headings at body size
and lists inline because @tailwindcss/typography was never installed/enabled
under Tailwind v4. Add the plugin and load it via '@plugin' in global.css so the
prose class produces markdown-like heading hierarchy, list styling, and
consistent typography.

Author: nsheff

site/package-lock.json

@@ -13,6 +13,7 @@
     "astro": "astro"
   },
   "dependencies": {
+    "@tailwindcss/typography": "^0.5.20",
     "@tailwindcss/vite": "^4.3.0",
     "astro": "^6.3.6",
     "tailwindcss": "^4.3.0",

site/package.json

@@ -1 +1,2 @@
-@import "tailwindcss";
+@import "tailwindcss";
+@plugin "@tailwindcss/typography";