Redesign Minimal Light header and hero — nav bar, warm accent, dashed-circle hero

Adds a horizontal nav (Home/Menu/Reservation), site search, and a Log in button (replacing drawer-based login access) to Minimal Light's header. Repoints --ml-accent to the existing dish_dash_accent_color option (warm orange, zero ripple into Khana Khazana). Rebuilds the hero with a dashed-circle photo frame, floating card, hours line, and dual CTA buttons (replacing the previous text-link CTA style) — all still driven by existing Homepage Settings fields.

See RELEASE.md v3.18.44 for full detail, and investigation-ml-header-hero-redesign.md for the pre-work investigation.