Realtime updates - Update fails sometimes when queuing multiple sites

### Platform

Docker container v0.52.1

### Issue

Since updating to 0.52.1 I noticed that queuing multiple sites to be checked (with the "Recheck all in xxx" button) usually results in some of them spinning forever, stuck on "Checking now"

If I manually refresh the page, usually I find that the check actually did complete, but the UI just never updated to reflect that.

Once in a while, an error like this appears

```
Exception: Brotli compression subprocess failed for /datastore/xxx/last-fetched.br
```

I ran `docker logs -f changedetection-io` and saw this error

The red underlined UUID does correspond to one of the sites that was spinning endlessly, so it seems related.

The URL for that site is: `https://pkgs.tailscale.com/stable/#macos` and it is using the default Fetcher (system default) and no filters/triggers.

Let me know if you need any more info!

Start by reproducing the failure with the “Recheck all in xxx” button for multiple sites, then follow `docker logs -f changedetection-io` and the reported Brotli compression subprocess error. Trace the affected site UUID and the realtime update path for the default Fetcher; done means queued checks stop spinning, completed checks appear without a manual refresh, and the reported error no longer occurs.

Written by the indexing model from the issue text.