Adds a Website settings tab (hero image, phone, WhatsApp, email) that
feeds the navbar, footer and contact page via a new SiteSettingsContext,
redesigns the navbar with a bigger centered logo plus phone/WhatsApp/shop
links, and adds a VIN/chassis-number field to the contact form, admin
inbox and notification email.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
