fix(mobiel): <fieldset> in admin forms doesn't shrink → entire form too wide
Root cause deeper than the links row: a <fieldset> has UA default
min-inline-size:min-content and therefore won't shrink below its content → on
Appearance (admin-site-edit) the entire form (Identity/Behaviour) overflowed off
screen on mobile. Fix: min-width:0 on .site-form + fieldsets + form fields, and
max-width:100%/border-box on inputs. Also admin-seo (same .site-form/fieldsets)
proactively fixed. Measured: Identity fieldset 424→≤360px.
Co-Authored-By: Claude <noreply@…>