refactor: pass api_url through context (#457)

* refactor: pass `api_url` through context

* 移除 LinkArgs.HttpReq

* pref(alias): 减少不必要下载代理

* 修复bug

* net: 支持1并发 分片下载

server/common/common.go

@@ -1,8 +1,6 @@
 package common
 
 import (
-	"context"
-	"net/http"
 	"strings"
 
 	"github.com/OpenListTeam/OpenList/cmd/flags"
@@ -90,10 +88,3 @@ func Pluralize(count int, singular, plural string) string {
 	}
 	return plural
 }
-
-func GetHttpReq(ctx context.Context) *http.Request {
-	if c, ok := ctx.(*gin.Context); ok {
-		return c.Request
-	}
-	return nil
-}