Replace RewardGrantService + ICurrencySpendService with IInventoryService tx.
CommitAsync's currency-collision rule replaces the manual Crystal RemoveAll+re-append
scrub in BuyPremiumAsync. AddPointsAsync uses result.Deltas for NewlyClaimed to
preserve per-track visibility (two Rupy grants stay two entries).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>