Verify `autoInjectSentryLabel` works in Expo build pipeline

[antonis]

Expo uses babel.config.js rather than the Metro transformer path to configure the component annotate plugin. The #6098 autoInjectSentryLabel option needs to work in both flows.

What to verify:

1. Expo apps using the Sentry Expo plugin pick up the new option correctly
2. The sentry-label injection works at build time in an Expo managed workflow
3. The sentry-label injection works in an Expo bare workflow
4. No build errors or unexpected behavior

How to test:

• Use the Expo sample app at samples/expo/
• Enable autoInjectSentryLabel in the Babel config
• Build and verify that static text children produce sentry-label props at runtime

Could be combined with the Metro config enablement task or done as a separate verification pass.

[linear-code]

RN-616