Template Builder — fail fast with a clear message for slow External Proxy reports

Template Builder now fails fast when data from an external source is too slow to load in the live preview. Previously, a slow provider (such as Amazon Sponsored Television) could leave the preview spinning for minutes before showing a generic timeout. Now, within seconds, the editor shows a clear message: the data is taking longer to retrieve than the live preview can wait, and to get it, you can run a report using the template or create a dashboard from it so the system collects and stores the data — after which it appears in the preview. No setup or configuration is required, and this applies to any slow external data source, not just one provider.