Users should be notified if imagery is currently being transferred internally

[spwoodcock]

Issue

1. User clicks to 'Verify' imagery and marks an area as fully flown (this triggers a transfer of imagery from S3 path under project_id/user-uploads to the task area directory project_id/task_id/images).
2. The user is pretty keen and moves straight to the Processing dialog. There is a slightly delay while the mentioned transfer happens (a few minutes), but the user does not know this is taking place).
3. They are blocked from clicking 'Process' for their task area, but don't know why.

Solution

1. Better information for the user to see that the task is having it's imagery 'Backed Up' after verifying it.
2. Provide 100% certainty we can't trigger processing before this step is done, else we may miss imagery to input into the ODM run (from the destination S3 path).
3. Enable the processing button for the user. Currently they must refresh the page, but there is no information to say that's needed and it's a bad user experience. Add another mechanism to enable the button in the UI.

[linear]

TECH-1240