fix: 修复Flutter资产页面API接口字段名称不匹配问题

主要修改:
1. AssetService.java - 修改getOverview()方法返回字段
   - totalAssets → totalAsset (总资产)
   - tradeValue → tradeBalance (交易余额)
   - 新增 totalProfit 字段 (总盈亏)
   - 移除 fundFrozen 和 positions 字段 (Flutter不需要)

2. 新增诊断工具和文档:
   - ASSET_API_DIAGNOSIS.md - API接口问题诊断报告
   - DATABASE_SCHEMA.md - 数据库表结构说明
   - test_asset_api.sh - API接口测试脚本
   - query_fund_accounts.sh - 用户资金账户查询脚本
   - fix_asset_api.sh - 自动修复脚本

修复后API返回格式:
{
  "totalAsset": 15500.0,      // 总资产
  "fundBalance": 15500.0,     // 资金余额
  "tradeBalance": 0,          // 交易余额
  "totalProfit": 0            // 总盈亏
}

影响范围:
- Flutter前端资产页面现在可以正确显示用户资产
- 充值审批后余额正确更新
- 资金账户数据查询正常

src/main/java/com/it/rattan/monisuo/service/AssetService.java

@@ -44,12 +44,13 @@ public class AssetService {
 
         // 资金账户
         AccountFund fund = getOrCreateFundAccount(userId);
-        result.put("fundBalance", fund.getBalance());
-        result.put("fundFrozen", fund.getFrozen());
+        BigDecimal fundBalance = fund.getBalance();
+        result.put("fundBalance", fundBalance);
 
         // 交易账户
-        BigDecimal tradeValue = BigDecimal.ZERO;
-        List<Map<String, Object>> positions = new ArrayList<>();
+        BigDecimal tradeBalance = BigDecimal.ZERO;
+        BigDecimal totalCost = BigDecimal.ZERO;  // 累计成本
+        BigDecimal totalValue = BigDecimal.ZERO; // 当前价值
 
         LambdaQueryWrapper<AccountTrade> wrapper = new LambdaQueryWrapper<>();
         wrapper.eq(AccountTrade::getUserId, userId)
@@ -61,25 +62,24 @@ public class AssetService {
             if (coin != null) {
                 BigDecimal value = trade.getQuantity().multiply(coin.getPrice())
                         .setScale(8, RoundingMode.DOWN);
-                tradeValue = tradeValue.add(value);
+                tradeBalance = tradeBalance.add(value);
 
-                Map<String, Object> position = new HashMap<>();
-                position.put("coinCode", trade.getCoinCode());
-                position.put("coinName", coin.getName());
-                position.put("quantity", trade.getQuantity());
-                position.put("price", coin.getPrice());
-                position.put("value", value);
-                position.put("avgPrice", trade.getAvgPrice());
-                positions.add(position);
+                // 计算成本和盈亏
+                BigDecimal cost = trade.getQuantity().multiply(trade.getAvgPrice());
+                totalCost = totalCost.add(cost);
+                totalValue = totalValue.add(value);
             }
         }
 
-        result.put("tradeValue", tradeValue);
-        result.put("positions", positions);
+        result.put("tradeBalance", tradeBalance);
 
         // 总资产
-        BigDecimal totalAssets = fund.getBalance().add(tradeValue);
-        result.put("totalAssets", totalAssets);
+        BigDecimal totalAsset = fundBalance.add(tradeBalance);
+        result.put("totalAsset", totalAsset);
+
+        // 总盈亏 = 当前价值 - 累计成本
+        BigDecimal totalProfit = totalValue.subtract(totalCost);
+        result.put("totalProfit", totalProfit);
 
         return result;
     }