Preview IaC resource changes

ryvn plan is now supported for all resource kinds instead of being limited to just Blueprints. ryvn plan enables you to preview changes made to IaC resources and surfaces notices and effects that those changes will have. This provides more guardrails and safety, especially when using agents for helping you configure Ryvn resources. If you have resources checked in and synced from Git, a plan is automatically run and output is shown as a pull request comment.