refactor(web): self-host fonts via next/font/google

Replace external <link> to fonts.googleapis.com with next/font/google
for Cormorant Garamond and Inter. Fonts are now built-time downloaded
and served from /_next/static/media, exposed via --font-serif and
--font-sans CSS variables that Tailwind's fontFamily reads.

Eliminates runtime dependency on Google Fonts CDN (helpful for offline
or region-restricted deploys), avoids FOUT through next/font's
size-adjusted fallback, and removes two render-blocking external
stylesheet requests on first load.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/tailwind.config.ts

@@ -24,8 +24,8 @@ const config: Config = {
         },
       },
       fontFamily: {
-        serif: ['"Cormorant Garamond"', '"Source Han Serif SC"', "ui-serif", "Georgia", "serif"],
-        sans: ['"Inter"', '"PingFang SC"', "ui-sans-serif", "system-ui", "sans-serif"],
+        serif: ['var(--font-serif)', '"Source Han Serif SC"', "ui-serif", "Georgia", "serif"],
+        sans: ['var(--font-sans)', '"PingFang SC"', "ui-sans-serif", "system-ui", "sans-serif"],
       },
       letterSpacing: {
         widest: "0.32em",