Refactor ETH balance and gas fee checks in SpotBot

- Updated balance checks to utilize user-defined thresholds for minimum trading and swap balances, enhancing flexibility.
- Improved gas fee validation by incorporating user settings, allowing for more personalized transaction management.
- Enhanced logging to provide clearer messages regarding balance sufficiency and gas fee limits, improving user feedback during operations.

src/Managing.Application/Bots/Grains/AgentGrain.cs

@@ -410,7 +410,9 @@ public class AgentGrain : Grain, IAgentGrain
         }
 
         // If ETH balance is sufficient, return success
-        if (balanceData.EthValueInUsd >= Constants.GMX.Config.MinimumTradeEthBalanceUsd)
+        // Use user's low ETH alert threshold as the minimum trading balance
+        var minTradeEthBalance = user.LowEthAmountAlert ?? Constants.GMX.Config.MinimumTradeEthBalanceUsd;
+        if (balanceData.EthValueInUsd >= minTradeEthBalance)
         {
             return new BalanceCheckResult
             {
@@ -421,13 +423,15 @@ public class AgentGrain : Grain, IAgentGrain
             };
         }
 
-        if (balanceData.EthValueInUsd < Constants.GMX.Config.MinimumSwapEthBalanceUsd)
+        // Check if ETH is below absolute minimum (half of the alert threshold)
+        var minSwapEthBalance = minTradeEthBalance * 0.67m; // 67% of alert threshold
+        if (balanceData.EthValueInUsd < minSwapEthBalance)
         {
             return new BalanceCheckResult
             {
                 IsSuccessful = false,
                 FailureReason = BalanceCheckFailureReason.InsufficientEthBelowMinimum,
-                Message = "ETH balance below minimum required amount",
+                Message = $"ETH balance below minimum required amount ({minSwapEthBalance:F2} USD)",
                 ShouldStopBot = true
             };
         }