Re-enable extension generation E2E

[alfonso-noriega]

WHY are these changes introduced?

The app scaffold E2E suite had a skipped generate extensions and build test. The skip was tied to an old product_subscription_ui template path that is no longer present in the current extension template list and previously drove the test into Business Platform Organizations gating/auth behavior.

WHAT is this pull request doing?

Re-enables the E2E and updates the subscription-related generated extension to use the current subscription_link_extension template. The test still generates a subscription-related extension plus a theme app extension, then builds the app.

How to test your changes?

• cd packages/e2e && pnpm tsc --noEmit
• cd packages/e2e && pnpm eslint "setup/**/*.ts" "helpers/**/*.ts" "tests/**/*.ts" "*.ts"
• node bin/run-knip-ci.js

Note: ESLint completed successfully with existing Nx project graph cache warnings for @nx/enforce-module-boundaries. The PR E2E job will run the re-enabled network test with CI credentials.

Post-release steps

None.

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've considered analytics changes to measure impact
• The change is not user-facing; no changeset is needed.