feat: 添加限流触发日志

backend/internal/ratelimit/middleware.go

@@ -5,6 +5,8 @@ import (
 	"net/http"
 
 	"github.com/gin-gonic/gin"
+
+	"github.com/hhs/camtalk/internal/trace"
 )
 
 // Middleware 返回 Gin 中间件，按 key 维度限流。
@@ -26,6 +28,13 @@ func Middleware(limiter Limiter, keyFunc func(*gin.Context) string) gin.HandlerF
 		allowed, retryAfter := limiter.Allow(c.Request.Context(), key)
 
 		if !allowed {
+			log := trace.FromContext(c.Request.Context())
+			log.Warnw("rate limited",
+				"client_ip", c.ClientIP(),
+				"path", c.Request.URL.Path,
+				"limit_key", key,
+				"retry_after_sec", int(retryAfter.Seconds()+0.5))
+
 			// 设置 Retry-After header（秒）
 			c.Header("Retry-After", fmt.Sprintf("%d", int(retryAfter.Seconds()+0.5)))