Add treatmentplan to settings form

We want the user to be able to both view the plan but also alter it.
## Must haves:
- A view or modal in the settings apge to render the plan, perhaps a btn that navigates to the view.
- Ability to change certain aspects of the plan like first dose of the day etc etc

nice to have:
abiity to change and alter every little tiny aspect of the plan

Start by locating the settings form and the treatment plan entry point. Trace how the plan is represented, then define which plan fields the settings view should render and allow users to change. Done means users can view the plan from settings and alter the agreed core fields; changing every aspect is optional.

Written by the indexing model from the issue text.