Redmine

Several documents under doc/ use commands such as rake, bundle exec rake, or the rails command for running tasks. This patch updates those examples to use bin/rails instead.

bin/rails is the standard command entry point in recent Rails versions. Because it runs commands in the context of the application's own Gemfile and Bundler environment, it eliminates the need for bundle exec, helps reduce environment-related errors, and makes the documented commands easier for users to follow.