Wires a localStorage/cookie-backed guest cart (per AI_PROMPT.md contract) into
the header cart icon and popup, with add-to-cart in the product card and buy
panel resolved via the dedicated by-product store-items endpoint. Continue
always hands off to the Meshkee customer dashboard for auth/checkout — no
login, register, or payment UI is built on the storefront.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
