fix: 修复最大仓位金额未生效和交易receipt解析问题

1. 修复 CopyTradingFilterService 中最大仓位金额(maxPositionValue)未生效的问题
   - 当只配置了最大仓位金额但未配置 maxSpread 或 minOrderDepth 时，
     仓位检查被跳过导致过滤失效
   - 将仓位检查移到 needOrderbook 判断之前，确保始终执行仓位检查

2. 修复 OnChainWsService 中交易 receipt 为 JsonNull 时的空指针问题
   - 添加 JsonNull 检查，防止解析失败时出现异常

backend/src/main/kotlin/com/wrbug/polymarketbot/service/copytrading/configs/CopyTradingFilterService.kt

@@ -71,12 +71,20 @@ class CopyTradingFilterService(
             }
         }
         
-        // 3. 检查是否需要获取订单簿
+        // 3. 检查是否需要获取订单簿或需要执行仓位检查
-        // 只有在配置了需要订单簿的过滤条件时才获取
+        // 只有在配置了需要订单簿的过滤条件时才获取订单簿
         val needOrderbook = copyTrading.maxSpread != null || copyTrading.minOrderDepth != null
         
+        // 3.5. 如果不需要订单簿，则跳过订单簿相关的检查，但仍然需要检查仓位限制
         if (!needOrderbook) {
-            // 不需要订单簿，直接通过
+            // 仓位检查（如果配置了最大仓位限制且提供了跟单金额和市场ID）
+            if (copyOrderAmount != null && marketId != null) {
+                val positionCheck = checkPositionLimits(copyTrading, copyOrderAmount, marketId)
+                if (!positionCheck.isPassed) {
+                    return positionCheck
+                }
+            }
+            // 通过所有检查
             return FilterResult.passed()
         }
         

backend/src/main/kotlin/com/wrbug/polymarketbot/service/copytrading/monitor/OnChainWsService.kt

@@ -1,5 +1,6 @@
 package com.wrbug.polymarketbot.service.copytrading.monitor
 
+import com.google.gson.JsonNull
 import com.wrbug.polymarketbot.api.*
 import com.wrbug.polymarketbot.entity.Leader
 import com.wrbug.polymarketbot.repository.LeaderRepository
@@ -86,7 +87,12 @@ class OnChainWsService(
     /**
      * 处理 Leader 的交易
      */
-    private suspend fun handleLeaderTransaction(leaderId: Long, txHash: String, httpClient: OkHttpClient, rpcApi: EthereumRpcApi) {
+    private suspend fun handleLeaderTransaction(
+        leaderId: Long,
+        txHash: String,
+        httpClient: OkHttpClient,
+        rpcApi: EthereumRpcApi
+    ) {
         val leader = monitoredLeaders[leaderId] ?: return
 
         logger.debug("开始处理 Leader 交易: leaderId=$leaderId, txHash=$txHash, leaderAddress=${leader.leaderAddress}")
@@ -105,7 +111,7 @@ class OnChainWsService(
             }
 
             val receiptRpcResponse = receiptResponse.body()!!
-            if (receiptRpcResponse.error != null || receiptRpcResponse.result == null) {
+            if (receiptRpcResponse.error != null || receiptRpcResponse.result == null || receiptRpcResponse.result is JsonNull) {
                 logger.warn("交易 receipt 错误: leaderId=$leaderId, txHash=$txHash, error=${receiptRpcResponse.error}")
                 return
             }