fix(utxo): calculate min_trading_vol based on fixed tx fees

[shamardy]

Fixes #1567

This fix prevents swap failures on UTXO coins with high fixed fees (e.g., ZEC, RVN), where the HTLC spend fee could exceed the traded amount.

The min_trading_vol calculation is now enhanced:

For coins with a fixed fee rate, the minimum volume is set to 10x the estimated HTLC spend fee, ensuring it's always economical to complete the swap.
For coins with dynamic fees, the calculation remains based on the dust amount to preserve synchronous behavior.

[cipig]

default min_vol for ZEC before this PR was 0.0001, now it is 0.00496 (0.0496 for RVN)... idk how the 0.00496 is calculated, but trading exactly that min_volume works fine
makerpaymentspent: https://blockchair.com/zcash/transaction/24715490971e72a2f9a438f61cc4d93464a6241bde268707c69b61d71c4b08ff (got 0.004464 ZEC and payed 0.000496 ZEC txfee)
the default min_volume for dynamic fee coins, like LTC, is the same as before... 0.000546 LTC (= 10x dust)

[shamardy]

idk how the 0.00496 is calculated

minimum trading volume is now 10 * minimum fee needed to spend an HTLC and the minimum fee to speed an HTLC is the fee per kb * htlc spend tx size, and an HTLC spend transaction size is 496 bytes

[smk762]

Recalculated volumes sighted for UTXO coins as below. Non-UTXO included for reference / regression testing. Values compare dev branch responses to this branch.

        [
            {
                "min_trading_vol": "0.0001",
                "min_trading_vol_AFTER": "0.0001",
                "ticker": "ARRR"
            },
            {
                "ticker": "DOGE",,
                "min_trading_vol": "0.1",
                "min_trading_vol_AFTER": "0.1"
            },
            {
                "min_trading_vol": "0.000000000000000001",
                "min_trading_vol_AFTER": "0.000000000000000001",
                "ticker": "MATIC"
            },
            {
                "ticker": "ATOM"
                "min_trading_vol": "0.000001",
                "min_trading_vol_AFTER": "0.000001",
            },
            {
                "min_trading_vol": "0.0001",
                "min_trading_vol_AFTER": "0.0496",
                "ticker": "RVN"
            },
            {
                "min_trading_vol": "0.000546",
                "min_trading_vol_AFTER": "0.000546",
                "ticker": "LTC"
            }
        ]

[onur-ozkan]

LGTM other than a minor note.