Pending incoming transfers awaiting accept

Token-standard `TransferInstruction`s addressed to the key's party that no one has accepted yet — the deposit inbox. Empty for self-custody wallet parties, whose transfers live on their own participant and are invisible to the desk.

curl -X GET "https://example.com/wallet/incoming"

{  "transfers": [    {      "cid": "string",      "symbol": "cbtc",      "amount": "1.5",      "sender": "taker",      "instrumentId": "string"    }  ]}

{  "error": "string",  "code": "INSUFFICIENT_FUNDS"}