Google Play → Symfony Pro entitlement verification

Admin → Settings → Billing & purchases now requires:
1. Google Play Pro product ID
2. Android package name
3. Google Play service-account JSON key

The service account must have access to the Android app in Google Play Console and the Google Play Android Developer API must be enabled.

Authenticated mobile endpoints:
GET  /api/v1/billing/google-play/pro/config
POST /api/v1/billing/google-play/pro/verify

The verify endpoint checks the purchase token with Google Play before creating a lifetime Pro entitlement.
Only a SHA-256 hash of the purchase token is persisted.

New migration:
Version20260802140000

This update does not contain or modify .env.