feat(usage-log): 增加请求 User-Agent 记录

在使用记录中添加 user_agent 字段，用于记录 API 请求的 User-Agent 头信息，
便于分析客户端类型和调试。

变更内容：
- 新增数据库迁移 028_add_usage_logs_user_agent.sql
- 更新 UsageLog 模型和 Ent Schema 添加 user_agent 字段
- 更新 Repository 层的 Create 和 scanUsageLog 方法
- 更新 RecordUsageInput 结构体支持传入 UserAgent
- 更新 Claude/OpenAI/Gemini 三个网关 Handler 传递 UserAgent

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/internal/handler/gateway_handler.go

@@ -108,6 +108,9 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 	// 获取订阅信息（可能为nil）- 提前获取用于后续检查
 	subscription, _ := middleware2.GetSubscriptionFromContext(c)
 
+	// 获取 User-Agent
+	userAgent := c.Request.UserAgent()
+
 	// 0. 检查wait队列是否已满
 	maxWait := service.CalculateMaxWait(subject.Concurrency)
 	canWait, err := h.concurrencyHelper.IncrementWaitCount(c.Request.Context(), subject.UserID, maxWait)
@@ -267,7 +270,7 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 			}
 
 			// 异步记录使用量（subscription已在函数开头获取）
-			go func(result *service.ForwardResult, usedAccount *service.Account) {
+			go func(result *service.ForwardResult, usedAccount *service.Account, ua string) {
 				ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
 				defer cancel()
 				if err := h.gatewayService.RecordUsage(ctx, &service.RecordUsageInput{
@@ -276,10 +279,11 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 					User:         apiKey.User,
 					Account:      usedAccount,
 					Subscription: subscription,
+					UserAgent:    ua,
 				}); err != nil {
 					log.Printf("Record usage failed: %v", err)
 				}
-			}(result, account)
+			}(result, account, userAgent)
 			return
 		}
 	}
@@ -394,7 +398,7 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 		}
 
 		// 异步记录使用量（subscription已在函数开头获取）
-		go func(result *service.ForwardResult, usedAccount *service.Account) {
+		go func(result *service.ForwardResult, usedAccount *service.Account, ua string) {
 			ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
 			defer cancel()
 			if err := h.gatewayService.RecordUsage(ctx, &service.RecordUsageInput{
@@ -403,10 +407,11 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 				User:         apiKey.User,
 				Account:      usedAccount,
 				Subscription: subscription,
+				UserAgent:    ua,
 			}); err != nil {
 				log.Printf("Record usage failed: %v", err)
 			}
-		}(result, account)
+		}(result, account, userAgent)
 		return
 	}
 }

backend/internal/handler/gemini_v1beta_handler.go

@@ -164,6 +164,9 @@ func (h *GatewayHandler) GeminiV1BetaModels(c *gin.Context) {
 	// Get subscription (may be nil)
 	subscription, _ := middleware.GetSubscriptionFromContext(c)
 
+	// 获取 User-Agent
+	userAgent := c.Request.UserAgent()
+
 	// For Gemini native API, do not send Claude-style ping frames.
 	geminiConcurrency := NewConcurrencyHelper(h.concurrencyHelper.concurrencyService, SSEPingFormatNone, 0)
 
@@ -300,7 +303,7 @@ func (h *GatewayHandler) GeminiV1BetaModels(c *gin.Context) {
 		}
 
 		// 6) record usage async
-		go func(result *service.ForwardResult, usedAccount *service.Account) {
+		go func(result *service.ForwardResult, usedAccount *service.Account, ua string) {
 			ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
 			defer cancel()
 			if err := h.gatewayService.RecordUsage(ctx, &service.RecordUsageInput{
@@ -309,10 +312,11 @@ func (h *GatewayHandler) GeminiV1BetaModels(c *gin.Context) {
 				User:         apiKey.User,
 				Account:      usedAccount,
 				Subscription: subscription,
+				UserAgent:    ua,
 			}); err != nil {
 				log.Printf("Record usage failed: %v", err)
 			}
-		}(result, account)
+		}(result, account, userAgent)
 		return
 	}
 }

backend/internal/handler/openai_gateway_handler.go

@@ -242,7 +242,7 @@ func (h *OpenAIGatewayHandler) Responses(c *gin.Context) {
 		}
 
 		// Async record usage
-		go func(result *service.OpenAIForwardResult, usedAccount *service.Account) {
+		go func(result *service.OpenAIForwardResult, usedAccount *service.Account, ua string) {
 			ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
 			defer cancel()
 			if err := h.gatewayService.RecordUsage(ctx, &service.OpenAIRecordUsageInput{
@@ -251,10 +251,11 @@ func (h *OpenAIGatewayHandler) Responses(c *gin.Context) {
 				User:         apiKey.User,
 				Account:      usedAccount,
 				Subscription: subscription,
+				UserAgent:    ua,
 			}); err != nil {
 				log.Printf("Record usage failed: %v", err)
 			}
-		}(result, account)
+		}(result, account, userAgent)
 		return
 	}
 }