feat(landing): use local fonts instead of Google Fonts

- Download Poppins and Bai Jamjuree font files locally
- Convert from next/font/google to next/font/local
- Enables builds in sandboxed environments without network access

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

nix/landing.nix

@@ -9,9 +9,6 @@ pkgs.buildNpmPackage {
   npmFlags = [ "--legacy-peer-deps" ];
   makeCacheWritable = true;
 
-  # Allow network access for Google Fonts fetching during Next.js build
-  __noChroot = true;
-
   nativeBuildInputs = with pkgs; [
     nodejs_22
     nodePackages.npm