Add typography system with Public Sans and 16 type styles

Self-host Public Sans via @fontsource-variable (weights 100-900, normal
+ italic). Add 6 composed @utility classes in typography.css for styles
that combine multiple properties (body-strong, small-strong, label,
overline, body-link, small-link). Matching text styles created in the
Figma design file via MCP for designer use.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -12,6 +12,7 @@
     "build-storybook": "storybook build"
   },
   "dependencies": {
+    "@fontsource-variable/public-sans": "^5.2.7",
     "@tailwindcss/vite": "^4.3.0",
     "clsx": "^2.1.1",
     "react": "^19.2.6",