feat: allow reordering exercises in the active workout

[armen-kocharyan]

Add Move up / Move down actions to each exercise's menu on the session screen, moving both recordedExercises and the blueprint's exercises in lockstep via new Session.withExerciseMovedUp/Down.

[github-actions]

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[armen-kocharyan]

* Make sure this PR follows an issue/feature request that's already been accepted as wanted (see [Contributing](https://github.com/LiamMorrow/LiftLog/blob/main/CONTRIBUTING.md)).

I apologize for not creating an issue/feature request first. I overlooked that instruction in CONTRIBUTING.md.
In the meantime, I suggest adding a check to the checklist in the "Pull Request Checklist" section to state that requirement even more clearly.