fix: 修复反向代理下客户端 IP 获取错误

backend/internal/handler/gemini_v1beta_handler.go

@@ -12,6 +12,7 @@ import (
 	"github.com/Wei-Shaw/sub2api/internal/pkg/antigravity"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/gemini"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/googleapi"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/ip"
 	"github.com/Wei-Shaw/sub2api/internal/server/middleware"
 	"github.com/Wei-Shaw/sub2api/internal/service"
 
@@ -316,7 +317,7 @@ func (h *GatewayHandler) GeminiV1BetaModels(c *gin.Context) {
 
 		// 捕获请求信息（用于异步记录，避免在 goroutine 中访问 gin.Context）
 		userAgent := c.GetHeader("User-Agent")
-		clientIP := c.ClientIP()
+		clientIP := ip.GetClientIP(c)
 
 		// 6) record usage async
 		go func(result *service.ForwardResult, usedAccount *service.Account, ua, ip string) {