* feat(ui): add error handling for enqueueBatch route, remove sessions
This re-implements the handling for the session create/invoke errors, but for batches.
Also remove all references to the old sessions routes in the UI.
* feat(ui): improve canvas image error UI
* make canvas error state gray instead of red
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Co-authored-by: Mary Hipp <maryhipp@Marys-MacBook-Air.local>