Creates a secure listing PSBT per listing, for the seller to sign and submit to POST /list/secure. No listing PSBT (SINGLE|ANYONECANPAY) is built: the listings are bought only through POST /intent/secure-purchase. All listings must share sellerOrdAddress and sellerReceiveAddress, and a request cannot mix inscriptions and runes. A request with TAP token transfers returns 400 with errorCode: "SECURE_LISTING_UNSUPPORTED", and nothing is built for the rest: list those with POST /intent/bulk-sell and the others here. sellerPaymentAddress and sellerPaymentPublicKey are ignored.