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-lock.json

@@ -8,6 +8,7 @@
       "name": "sdc-frontend",
       "version": "0.0.0",
       "dependencies": {
+        "@fontsource-variable/public-sans": "^5.2.7",
         "@tailwindcss/vite": "^4.3.0",
         "clsx": "^2.1.1",
         "react": "^19.2.6",
@@ -915,6 +916,15 @@
         "node": "^20.19.0 || ^22.13.0 || >=24"
       }
     },
+    "node_modules/@fontsource-variable/public-sans": {
+      "version": "5.2.7",
+      "resolved": "https://registry.npmjs.org/@fontsource-variable/public-sans/-/public-sans-5.2.7.tgz",
+      "integrity": "sha512-4mvade2J3slKkvwRkS+p8T3szet/0vhWoSnuUJTVU81Uo2pRpSZY/Y8bSLRqpSwzIPxjVmRJ53oq6JKP/l/PSg==",
+      "license": "OFL-1.1",
+      "funding": {
+        "url": "https://github.com/sponsors/ayuhito"
+      }
+    },
     "node_modules/@humanfs/core": {
       "version": "0.19.2",
       "resolved": "https://registry.npmjs.org/@humanfs/core/-/core-0.19.2.tgz",