Choose specific app versions/docker image during installation or update

Problem/Justification
TrueNAS Scale lacks the option to choose specific app versions during installation. This limits flexibility, especially when new updates cause issues, like bugs or incompatibilities. Users can’t revert to a stable version easily.

Impact
Allowing version selection would improve control, reliability, and reduce risks from faulty or unwanted updates.

User Story
For example, Transmission 4.0.6 is banned from some trackers, so I should be able to easily install a previous version (e.g., 4.0.5) to continue using the app without disruption.