feat: added banner and update subscription check to make maintained actions free for public repos

[sailikhith-stepsecurity]

Summary

• Added StepSecurity Maintained Action banner to README.md
• Updated subscription validation: public repositories are now free (no API check)
• Upgraded Node.js runtime to node24 (action.yml)
• Updated workflow files with configurable node_version input (if applicable)

Changes by type

• TypeScript/JS actions: replaced validateSubscription() body, updated action.yml to node24, rebuilt dist/
• Docker/Shell actions: replaced entrypoint.sh subscription block
• Composite actions: added Subscription check step to action.yml

Verification

• Subscription check skips for public repos
• Subscription check fires for private repos
• README banner is present at the top
• Build passes (TS/JS actions)

Auto-generated by StepSecurity update-propagator. Task ID: 20260325T061937Z