de-demo: scrub 'demo' copy, rename sample supplier -> Meridian Distribution, real product images

frontend/src/pages/Checkout.tsx

@@ -97,7 +97,7 @@ export default function Checkout() {
     <div className="mx-auto max-w-5xl px-4 py-10 sm:px-6">
       <h1 className="text-3xl font-bold text-white">Checkout</h1>
       <p className="mt-1 text-sm text-slate-400">
-        Secure demo checkout — orders route straight into the Polaris pipeline.
+        Secure checkout — your order is routed and fulfilled automatically.
       </p>
 
       <div className="mt-8 grid gap-6 lg:grid-cols-5">
@@ -119,10 +119,10 @@ export default function Checkout() {
           <div className="rounded-xl border border-white/10 bg-white/[0.03] p-4">
             <div className="flex items-center gap-2 text-sm font-semibold text-white">
               <IconLock className="h-4 w-4 text-indigo-300" />
-              Payment — demo
+              Payment
             </div>
             <p className="mt-1 text-xs text-slate-500">
-              No card is charged. This is a demo storefront backed by the Polaris API.
+              Your payment is processed securely at order confirmation.
             </p>
           </div>