fix: switch Google Fonts to runtime <link> tags for build environments without internet

- Replace next/font/google with <link> tags in <head> (loads fonts client-side at runtime)
- Define --font-nunito and --font-pixel CSS variables in globals.css with font-family fallbacks
- Remove @prisma/client from serverExternalPackages in next.config.ts (devDep only)

src/app/globals.css

@@ -4,6 +4,11 @@
 @plugin "tailwindcss-animate";
 @custom-variant dark (&:where(.dark, .dark *));
 
+:root {
+	--font-nunito: "Nunito", ui-sans-serif, system-ui, -apple-system, "Segoe UI", sans-serif;
+	--font-pixel: "Pixelify Sans", monospace;
+}
+
 @theme {
 	--font-sans:
 		var(--font-nunito), "Nunito", ui-sans-serif, system-ui, -apple-system,