chore: use stdlib uuid package

Go 1.27 ships a uuid package with the same API, dropping the direct
dependency on github.com/google/uuid.

Assisted-by: Claude:Opus 5

services/auth/reverseproxy.go

@@ -14,7 +14,7 @@ import (
 	"gitea.dev/modules/session"
 	"gitea.dev/modules/setting"
 
-	gouuid "github.com/google/uuid"
+	"uuid"
 )
 
 // Ensure the struct implements the interface.
@@ -143,7 +143,7 @@ func (r *ReverseProxy) newUser(req *http.Request) *user_model.User {
 		return nil
 	}
 
-	email := gouuid.New().String() + "@localhost"
+	email := uuid.New().String() + "@localhost"
 	if setting.Service.EnableReverseProxyEmail {
 		webAuthEmail := req.Header.Get(setting.ReverseProxyAuthEmail)
 		if len(webAuthEmail) > 0 {