fix(api): use UUID to ensure traderID uniqueness (#893) (#1008)

## Problem
When multiple users create traders with the same exchange + AI model
combination within the same second, they generate identical traderIDs,
causing data conflicts.
Old code (Line 496):
```go
traderID := fmt.Sprintf("%s_%s_%d", req.ExchangeID, req.AIModelID, time.Now().Unix())
```
## Solution
Use UUID to guarantee 100% uniqueness while preserving prefix for debugging:
```go
traderID := fmt.Sprintf("%s_%s_%s", req.ExchangeID, req.AIModelID, uuid.New().String())
```
Example output: `binance_gpt-4_a1b2c3d4-e5f6-7890-abcd-ef1234567890`
## Changes
- `api/server.go:495-497`: Use UUID for traderID generation
- `api/traderid_test.go`: New test file with 3 comprehensive tests
## Tests
✅ All tests passed (0.189s)
✅ TestTraderIDUniqueness - 100 unique IDs generated
✅ TestTraderIDFormat - 3 exchange/model combinations validated
✅ TestTraderIDNoCollision - 1000 iterations without collision
Fixes #893
Co-authored-by: the-dev-z <the-dev-z@users.noreply.github.com>

api/server.go

@@ -492,8 +492,9 @@ func (s *Server) handleCreateTrader(c *gin.Context) {
 		}
 	}
 
-	// 生成交易员ID
-	traderID := fmt.Sprintf("%s_%s_%d", req.ExchangeID, req.AIModelID, time.Now().Unix())
+	// 生成交易员ID (使用 UUID 确保唯一性，解决 Issue #893)
+	// 保留前缀以便调试和日志追踪
+	traderID := fmt.Sprintf("%s_%s_%s", req.ExchangeID, req.AIModelID, uuid.New().String())
 
 	// 设置默认值
 	isCrossMargin := true // 默认为全仓模式