Add a status-bar cluster, shown when connected over HTTP, that surfaces
the broker state and live acquisition info:
- broker state box (QProgressBar) with progress drawn as the bar fill,
polled ~1 Hz on its own timer independent of image sync
- Live/Disconnected connection badge (host:port in tooltip)
- "+N new" badge and effective live-rate (Hz) readout
All widgets are fixed-width and only blanked in place, so the bar never
reflows when things appear/disappear.
Add a third autoload mode (HTTPSyncDataset): manually selecting an image
while following live now freezes the displayed image but keeps the dataset,
plots and image count updating. Surfaced via a tri-state HTTP Sync button
(off / live / data-only).
Also fix GetBrokerStatus() dropping the message field and a couple of
copy-pasted exception strings in JFJochHttpReader.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>