What does this PR do?

This PR hides the promotion code view and button (BillingDiscountView component) for users on the Hobby plan. This ensures that discount-related UI elements are only displayed to users with an active paid subscription, aligning the UI with the new billing setup. The component now returns null if organization?.cloudConfig?.stripe?.activeSubscriptionId is not set.

Fixes # GTM-1441

Type of change

• Bug fix (non-breaking change which fixes an issue)
• Chore (refactoring code, technical debt, workflow improvements)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (does not change functionality, e.g. code style improvements, linting)
• This change requires a documentation update

Mandatory Tasks

• Make sure you have self-reviewed the code. A decent size PR without self-review might be rejected.

Checklist

• I haven't read the contributing guide
• My code doesn't follow the style guidelines of this project (pnpm run format)
• I haven't commented my code, particularly in hard-to-understand areas
• I haven't checked if my PR needs changes to the documentation
• I haven't checked if my changes generate no new warnings (npm run lint)
• I haven't added tests that prove my fix is effective or that my feature works
• I haven't checked if new and existing unit tests pass locally with my changes

Linear Issue: GTM-1441