fix(eth): use next-block base fee in simple EIP-1559 fee estimator

The simple fee-history estimator read `baseFeePerGas.first()`, which is
the oldest block of the eth_feeHistory window, not the latest: the array
is ordered oldest to newest and carries one extra trailing entry with
the next block's base fee. On chains with fast blocks (Gnosis: 5s), the
base fee can grow up to 12.5% per block, so a 5-block-stale base fee
made max_fee_per_gas fall below the current base fee during fee spikes.
Nethermind >= 1.36.0 strictly validates maxFeePerGas >= baseFee in
eth_estimateGas when fee fields are passed, rejecting such requests and
breaking order posting / trade preimage on Gnosis.

Use `.last()` (the next block's base fee on spec-compliant clients, or
the newest mined block on clients that omit the extra entry, e.g.
Avalanche and Fantom) and match Nethermind's pre-1.38.0 error message
"miner premium is negative" so it maps to GasFeeCapBelowBaseFee instead
of a raw transport error.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: shamardy

mm2src/coins/eth.rs

@@ -7562,6 +7562,8 @@ async fn get_eth_gas_details_from_withdraw_fee(
                 return MmError::err(EthGasDetailsErr::AmountTooLow { amount, threshold });
             } else if error_str.contains("fee cap less than block base fee")
                 || error_str.contains("max fee per gas less than block base fee")
+                // Nethermind < 1.38.0 reports a fee cap below the base fee with this message
+                || error_str.contains("miner premium is negative")
             {
                 if let Some((user_cap, required_base)) = parse_fee_cap_error(&error_str) {
                     // The RPC error gives fee values in wei. Convert to Gwei (9 decimals) for the user.

mm2src/coins/eth/fee_estimation/eip1559/simple.rs

@@ -133,12 +133,16 @@ impl FeePerGasSimpleEstimator {
 
     /// estimate priority fees by fee history
     fn calculate_with_history(coin: &EthCoin, fee_history: &FeeHistoryResult) -> Web3RpcResult<FeePerGasEstimated> {
-        // For estimation of max fee and max priority fee we use latest block base_fee but adjusted.
-        // Apparently for this simple fee estimator for assured high priority we should assume
-        // that the real base_fee may go up by 1,25 (i.e. if the block is full). This is covered by high priority ADJUST_MAX_FEE multiplier
+        // For estimation of max fee and max priority fee we use the next block base_fee but adjusted.
+        // `eth_feeHistory` returns `baseFeePerGas` ordered oldest to newest with one extra trailing entry
+        // for the next (pending) block, so the last element is the most recent value available.
+        // Note that some non-mainline clients (e.g. Avalanche, Fantom) omit the extra next-block entry,
+        // in which case the last element is the newest mined block's base fee.
+        // The ADJUST_BASE_FEE multipliers then add headroom on top in case the base fee keeps growing
+        // (it can go up by 12.5% per block if blocks are full) until the tx is included.
         let latest_base_fee = fee_history
             .base_fee_per_gas
-            .first()
+            .last()
             .cloned()
             .unwrap_or_else(|| U256::from(0));
         let latest_base_fee_dec = wei_to_gwei_decimal(latest_base_fee).unwrap_or_else(|_| BigDecimal::from(0));