fix(api): add balance sync endpoint with smart detection

## Summary
- Add POST /traders/:id/sync-balance endpoint (Option B)
- Add smart detection showing balance change percentage (Option C)
- Fix balance display bug caused by commit 2b9c4d2
## Changes
### api/server.go
- Add handleSyncBalance() handler
- Query actual exchange balance via trader.GetBalance()
- Calculate change percentage for smart detection
- Update initial_balance in database
- Reload trader into memory after update
### config/database.go
- Add UpdateTraderInitialBalance() method
- Update traders.initial_balance field
## Root Cause
Commit 2b9c4d2 auto-queries exchange balance at trader creation time,
but never updates after user deposits more funds, causing:
- Wrong initial_balance (400 USDT vs actual 3000 USDT)
- Wrong P&L calculations (-2598.55 USDT instead of actual)
## Solution
Provides manual sync API + smart detection to update initial_balance
when user deposits funds after trader creation.
Co-Authored-By: tinkle-community <tinklefund@gmail.com>

api/server.go

@@ -9,6 +9,7 @@ import (
 	"nofx/config"
 	"nofx/decision"
 	"nofx/manager"
+	"nofx/trader"
 	"strconv"
 	"strings"
 	"time"
@@ -109,6 +110,7 @@ func (s *Server) setupRoutes() {
 			protected.POST("/traders/:id/start", s.handleStartTrader)
 			protected.POST("/traders/:id/stop", s.handleStopTrader)
 			protected.PUT("/traders/:id/prompt", s.handleUpdateTraderPrompt)
+			protected.POST("/traders/:id/sync-balance", s.handleSyncBalance)
 
 			// AI模型配置
 			protected.GET("/models", s.handleGetModelConfigs)
@@ -641,6 +643,113 @@ func (s *Server) handleUpdateTraderPrompt(c *gin.Context) {
 	c.JSON(http.StatusOK, gin.H{"message": "自定义prompt已更新"})
 }
 
+// handleSyncBalance 同步交易所余额到initial_balance（选项B：手动同步 + 选项C：智能检测）
+func (s *Server) handleSyncBalance(c *gin.Context) {
+	userID := c.GetString("user_id")
+	traderID := c.Param("id")
+
+	log.Printf("🔄 用户 %s 请求同步交易员 %s 的余额", userID, traderID)
+
+	// 从数据库获取交易员配置（包含交易所信息）
+	traderConfig, _, exchangeCfg, err := s.database.GetTraderConfig(userID, traderID)
+	if err != nil {
+		c.JSON(http.StatusNotFound, gin.H{"error": "交易员不存在"})
+		return
+	}
+
+	if exchangeCfg == nil || !exchangeCfg.Enabled {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "交易所未配置或未启用"})
+		return
+	}
+
+	// 创建临时 trader 查询余额
+	var tempTrader trader.Trader
+	var createErr error
+
+	switch traderConfig.ExchangeID {
+	case "binance":
+		tempTrader = trader.NewFuturesTrader(exchangeCfg.APIKey, exchangeCfg.SecretKey)
+	case "hyperliquid":
+		tempTrader, createErr = trader.NewHyperliquidTrader(
+			exchangeCfg.APIKey,
+			exchangeCfg.HyperliquidWalletAddr,
+			exchangeCfg.Testnet,
+		)
+	case "aster":
+		tempTrader, createErr = trader.NewAsterTrader(
+			exchangeCfg.AsterUser,
+			exchangeCfg.AsterSigner,
+			exchangeCfg.AsterPrivateKey,
+		)
+	default:
+		c.JSON(http.StatusBadRequest, gin.H{"error": "不支持的交易所类型"})
+		return
+	}
+
+	if createErr != nil {
+		log.Printf("⚠️ 创建临时 trader 失败: %v", createErr)
+		c.JSON(http.StatusInternalServerError, gin.H{"error": fmt.Sprintf("连接交易所失败: %v", createErr)})
+		return
+	}
+
+	// 查询实际余额
+	balanceInfo, balanceErr := tempTrader.GetBalance()
+	if balanceErr != nil {
+		log.Printf("⚠️ 查询交易所余额失败: %v", balanceErr)
+		c.JSON(http.StatusInternalServerError, gin.H{"error": fmt.Sprintf("查询余额失败: %v", balanceErr)})
+		return
+	}
+
+	// 提取可用余额
+	var actualBalance float64
+	if availableBalance, ok := balanceInfo["available_balance"].(float64); ok && availableBalance > 0 {
+		actualBalance = availableBalance
+	} else if availableBalance, ok := balanceInfo["availableBalance"].(float64); ok && availableBalance > 0 {
+		actualBalance = availableBalance
+	} else if totalBalance, ok := balanceInfo["balance"].(float64); ok && totalBalance > 0 {
+		actualBalance = totalBalance
+	} else {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "无法获取可用余额"})
+		return
+	}
+
+	oldBalance := traderConfig.InitialBalance
+
+	// ✅ 选项C：智能检测余额变化
+	changePercent := ((actualBalance - oldBalance) / oldBalance) * 100
+	changeType := "增加"
+	if changePercent < 0 {
+		changeType = "减少"
+	}
+
+	log.Printf("✓ 查询到交易所实际余额: %.2f USDT (当前配置: %.2f USDT, 变化: %.2f%%)",
+		actualBalance, oldBalance, changePercent)
+
+	// 更新数据库中的 initial_balance
+	err = s.database.UpdateTraderInitialBalance(userID, traderID, actualBalance)
+	if err != nil {
+		log.Printf("❌ 更新initial_balance失败: %v", err)
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "更新余额失败"})
+		return
+	}
+
+	// 重新加载交易员到内存
+	err = s.traderManager.LoadUserTraders(s.database, userID)
+	if err != nil {
+		log.Printf("⚠️ 重新加载用户交易员到内存失败: %v", err)
+	}
+
+	log.Printf("✅ 已同步余额: %.2f → %.2f USDT (%s %.2f%%)", oldBalance, actualBalance, changeType, changePercent)
+
+	c.JSON(http.StatusOK, gin.H{
+		"message":        "余额同步成功",
+		"old_balance":    oldBalance,
+		"new_balance":    actualBalance,
+		"change_percent": changePercent,
+		"change_type":    changeType,
+	})
+}
+
 // handleGetModelConfigs 获取AI模型配置
 func (s *Server) handleGetModelConfigs(c *gin.Context) {
 	userID := c.GetString("user_id")