Fix method visibility issue by moving private directive to correct location

The private directive was incorrectly placed after append_to_spec_rails_helper,
making critical methods like add_react_on_rails_package, add_react_dependencies,
add_css_dependencies, and add_dev_dependencies private when they need to be
public for external generators to call them.

This was causing the install generator to fail because it couldn't access these
methods, leading to gem dependency conflicts during testing.

Moved private directive to its proper location after all public methods but
before private helper methods like handle_npm_failure.

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

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

Author: ihabadham

lib/generators/react_on_rails/base_generator.rb

@@ -128,8 +128,6 @@ def append_to_spec_rails_helper
         end
       end
 
-      private
-
       def add_react_on_rails_package
         major_minor_patch_only = /\A\d+\.\d+\.\d+\z/
 
@@ -229,6 +227,8 @@ def install_js_dependencies
         end
       STR
 
+      private
+
       def handle_npm_failure(dependency_type, packages, dev: false)
         install_command = dev ? "npm install --save-dev" : "npm install"
         GeneratorMessages.add_warning(<<~MSG.strip)