Fix CI build by excluding nokogiri in GitHub Actions/Act environments

nokogiri is a native extension gem that causes build failures in CI
environments due to Ruby version conflicts and missing native dependencies.
This restores the conditional exclusion for CI while keeping it available
for local development.

app/Gemfile

@@ -12,7 +12,8 @@ gem "fastlane", "~> 2.228.0"
 
 group :development do
   gem "dotenv"
-  gem "nokogiri", "~> 1.18.9", platform: :ruby
+  # Exclude nokogiri for GitHub Actions and Act
+  gem "nokogiri", "~> 1.18.9", platform: :ruby unless ENV["GITHUB_ACTIONS"] || ENV["ACT"]
 end
 
 plugins_path = File.join(File.dirname(__FILE__), "fastlane", "Pluginfile")