Add or edit a treatment

Goal: maintain the catalog every chart and wizard reads from.

You need: treatments settings access (admins/managers; dentists can view).

Steps:

1. Go to Settings → Treatments.
2. Click Add Treatment (or the pencil on an existing one).
3. Set name, category, and chart color (shows on the tooth chart and plan documents).
4. Set the clinical rules: Requires teeth? (off for things like whitening — quantity is used instead), allowed visits, and any incompatibilities.
5. Save. The treatment is immediately available on the tooth chart.

Translations: the name can be translated per patient language in the same dialog — patient pages use those.