Add Bundler check to prevent false Pro gem detection in sibling structure

In the sibling gem structure, both react_on_rails and react_on_rails_pro
gems are loaded from the root Gemfile, making both available via Gem.loaded_specs.

This caused the base dummy app to incorrectly detect Pro as installed, leading to:
- Package mismatch errors (base dummy has react-on-rails package, not Pro package)
- Potential double-engine loading issues

Solution: Check Bundler's actual dependencies to see if Pro is explicitly
requested in the application's Gemfile, not just if it's available in the load path.

This allows both gems to coexist in development while correctly identifying
which gem the application is actually using.

Author: justin808

lib/react_on_rails/utils.rb

@@ -248,16 +248,29 @@ def self.gem_available?(name)
       end
     end
 
+    # Checks if react_on_rails_pro is in the current Bundler context
+    # @return [Boolean] true if Pro gem is in the Gemfile
+    def self.pro_gem_in_bundle?
+      return true unless defined?(Bundler)
+
+      Bundler.locked_gems&.dependencies&.key?("react_on_rails_pro") ||
+        Bundler.definition.dependencies.any? { |dep| dep.name == "react_on_rails_pro" }
+    end
+
     # Checks if React on Rails Pro is installed and licensed.
     # This method validates the license and will raise an exception if invalid.
     #
+    # In a sibling gem structure, both gems may be loaded, but we should only
+    # consider Pro as "active" if it's explicitly requested in the application's Gemfile.
+    #
     # @return [Boolean] true if Pro is available with valid license
     # @raise [ReactOnRailsPro::Error] if license is invalid
     def self.react_on_rails_pro?
       return @react_on_rails_pro if defined?(@react_on_rails_pro)
 
       @react_on_rails_pro = begin
         return false unless gem_available?("react_on_rails_pro")
+        return false unless pro_gem_in_bundle?
 
         # Guard against edge cases where constant exists but module isn't fully loaded
         require "react_on_rails_pro" unless defined?(ReactOnRailsPro)