fix: add kconv gem for Ruby 3.4 compatibility in bare_rn

Ruby 3.4 removed kconv from its standard library. CocoaPods 1.15.x uses it
via CFPropertyList, causing pod install to fail. Adding the kconv gem
alongside the other Ruby 3.4 compat gems already in the Gemfile.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: msluszniak

apps/bare_rn/Gemfile

@@ -14,3 +14,4 @@ gem 'bigdecimal'
 gem 'logger'
 gem 'benchmark'
 gem 'mutex_m'
+gem 'kconv'