Show 'recorded prediction' next to 'working prediction'

The 'LangPro prediction' entailment label that was added in #130 should be moved.

Frontend changes
- There should be a field 'Recorded prediction' in the ProblemDetailsComponent that shows the entailment label that is currently saved to the database. This should be below the problem's entailment label (from the dataset).
- Another field 'Working prediction' shows the result of the latest 'Parse and Prove' run. There should be some style/animation to indicate that this label is not fixed but subject to change.
- After hitting 'Save problem', the working prediction label should replace the recorded prediction label.
- An information icon (with a modal) explains this behaviour to the user. The explanatory text underneath 'LangPro prediction' can go there as well.
- The 'Save problem' button should be moved back so it's next to the 'Parse and Prove' button again. The 'Copy problem' and 'Edit problem' buttons can stay where they are.

Start in the ProblemDetailsComponent and trace the existing LangPro prediction, Parse and Prove, Save problem, Copy problem, and Edit problem interactions. Done means recorded and working predictions are distinct with the requested update behavior, the explanation is available through an information modal, and the buttons are positioned as described.

Written by the indexing model from the issue text.