Add Transfer Proof Coverage to Universe Sync Integration Test

[ffranr]

Current integration tests only cover issuance proof syncing. The AssetLeaves RPC, which supports both issuance and transfer proofs, is not being tested for transfer proofs—confirmed by forcing it to reject transfers locally without any test failure.

This gap indicates that CI and itests never trigger AssetLeaves with transfer proofs.

The key helper here is AssertUniverseLeavesEqual.

To fix this, extend testUniverseSync to:

• Send a minted asset from the minting node to a secondary node
• Inspect universe leaves for transfer proofs
• Sync universe with a third node
• Assert all universes are synced, including transfer proofs