feat: License 支持筛选多选批量删除

仅已吊销或已过期可删，有效授权自动跳过；单条删除同步限制。

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/router/router.go

@@ -174,6 +174,7 @@ func SetupRouter(db *gorm.DB, cfg *config.Config) *gin.Engine {
 				register(licenses, "POST", "/offline", licenseController.IssueOffline)
 				register(licenses, "GET", "/offline/public-key", licenseController.OfflinePublicKey)
 				register(licenses, "GET", "/export", licenseController.Export)
+				register(licenses, "POST", "/batch-delete", licenseController.BatchDelete)
 				register(licenses, "GET", "/:id", licenseController.Get)
 				register(licenses, "PUT", "/:id", licenseController.Update)
 				register(licenses, "DELETE", "/:id", licenseController.Delete)