Gift notification fires before lamb2 ownership cache catches up — recipient opens an empty backpack

## Summary
The gift-received notification fires as soon as the transfer is chain-indexed, but the recipient's backpack contents come from lamb2, whose ownership cache lags by up to ~10 minutes. Recipients tap the notification and find no gift, then report the gifting flow as broken (#bug-reporting week of 2026-07-27, thread `gift-notification-too-early`).

## Root cause split
- **Client half (mitigated):** branch `bugsweep/gift-notification-too-early` updates the notification copy to set the arrival expectation ("may take a few minutes to appear in your backpack"). Copy-only by design.
- **Backend half (this issue):** the real fix is lamb2-side — evict or bypass the ownership cache for the recipient when a transfer is indexed, so the backpack reflects the gift when the notification lands. Without it the client mitigation only papers over the delay.

## Suggested direction
On transfer indexing, publish an invalidation for the recipient address to lamb2's ownership cache (or lower the TTL for addresses with pending inbound transfers). The notification pipeline already knows the recipient and the item at fire time.

🤖 Generated with [Claude Code](https://claude.com/claude-code)