Applied app-input/app-form-field/app-button to 9 of 11 Project Editor
sections: general, branding, theme, footer, homepage, widgets, languages,
navigation, preview. header and features sections were left unchanged -
they contain only checkboxes and selects, and no Checkbox/Select primitive
exists yet.
Theme section's 8 color pickers stay native <input type=color> (app-input's
type union doesn't include 'color') but are now wrapped in app-form-field
for consistent label/hint treatment. Added app-form-field.full grid-column
rule to section.shared.scss (shared by all 11 sections) alongside the
existing label.full rule, since the custom element doesn't match that
selector.
Production build green, arch:check passes.
