fix(ecommerce): deshabilitar compra y mostrar "Agotado" sin stock real

variant.available (calculado en lib/headless/providers/medusa.ts a
partir de manage_inventory/allow_backorder/inventory_quantity) ya
llegaba correcto hasta el componente, pero ningun boton de compra lo
usaba -- se podia seguir agregando al carrito un producto con stock 0.

Afecta product-purchase.tsx (pagina de producto), mobile-add-to-cart.tsx
(barra fija mobile) y product-card.tsx (tarjetas de catalogo): boton
deshabilitado + label "Agotado" en los tres, mas badge/overlay en la
tarjeta de catalogo.

workloads/ecommerce/components/product/product-purchase.tsx

@@ -1,6 +1,6 @@
 "use client";
 
-import { CheckCircle2, ShoppingBag, TriangleAlert, Truck } from "lucide-react";
+import { CheckCircle2, ShoppingBag, TriangleAlert, Truck, XCircle } from "lucide-react";
 import { useState } from "react";
 import { Button } from "@/components/ui/button";
 import type { Product } from "@/lib/headless/types";
@@ -11,12 +11,68 @@ export function ProductPurchase({ product }: { product: Product }) {
   const [variantId, setVariantId] = useState(product.variants[0]?.id);
   const addItem = useCartStore((state) => state.addItem);
   const selectedVariant = product.variants.find((variant) => variant.id === variantId) ?? product.variants[0];
+  const outOfStock = selectedVariant?.available === false;
   const lowStock =
+    !outOfStock &&
     selectedVariant?.inventoryQuantity !== null &&
     selectedVariant?.inventoryQuantity !== undefined &&
     selectedVariant.inventoryQuantity > 0 &&
     selectedVariant.inventoryQuantity <= LOW_STOCK_THRESHOLD
       ? selectedVariant.inventoryQuantity
       : null;
-  return <div><div className="mb-5 flex flex-wrap gap-2">{product.variants.map((variant) => <button key={variant.id} onClick={() => setVariantId(variant.id)} className={`rounded-full border px-4 py-2 text-sm font-bold ${variantId === variant.id ? "border-ari-marino bg-ari-marino text-white" : "border-slate-200"}`}>{variant.value}</button>)}</div><div className="mb-6 flex items-end gap-3"><strong className="text-3xl font-black">{formatMoney(product.price, product.currency)}</strong>{product.compareAtPrice && <del className="text-slate-400">{formatMoney(product.compareAtPrice, product.currency)}</del>}</div>{/* oculto en mobile: MobileAddToCart (barra fija abajo, lg:hidden) ya cubre esa misma accion ahi -- sin el hidden aqui, ambos se mostraban a la vez. */}<Button variant="primary" size="lg" className="hidden w-full lg:inline-flex" onClick={() => addItem(product, variantId)}><ShoppingBag />Añadir al carrito</Button><div className="mt-5 grid gap-3 rounded-2xl bg-slate-50 p-4 text-sm">{lowStock !== null ? <span className="flex items-center gap-2 font-bold text-amber-600"><TriangleAlert className="size-4" />Quedan {lowStock} unidades</span> : <span className="flex items-center gap-2 font-bold"><CheckCircle2 className="size-4 text-emerald-500" />Disponibilidad por confirmar</span>}<span className="flex items-center gap-2 font-bold"><Truck className="size-4 text-cyan-600" />Envíos nacionales</span></div></div>;
+
+  return (
+    <div>
+      <div className="mb-5 flex flex-wrap gap-2">
+        {product.variants.map((variant) => (
+          <button
+            key={variant.id}
+            onClick={() => setVariantId(variant.id)}
+            className={`rounded-full border px-4 py-2 text-sm font-bold ${
+              variantId === variant.id ? "border-ari-marino bg-ari-marino text-white" : "border-slate-200"
+            } ${variant.available === false ? "opacity-40" : ""}`}
+          >
+            {variant.value}
+          </button>
+        ))}
+      </div>
+      <div className="mb-6 flex items-end gap-3">
+        <strong className="text-3xl font-black">{formatMoney(product.price, product.currency)}</strong>
+        {product.compareAtPrice && <del className="text-slate-400">{formatMoney(product.compareAtPrice, product.currency)}</del>}
+      </div>
+      {/* oculto en mobile: MobileAddToCart (barra fija abajo, lg:hidden) ya cubre esa misma accion ahi -- sin el hidden aqui, ambos se mostraban a la vez. */}
+      <Button
+        variant="primary"
+        size="lg"
+        className="hidden w-full lg:inline-flex"
+        disabled={outOfStock}
+        onClick={() => addItem(product, variantId)}
+      >
+        <ShoppingBag />
+        {outOfStock ? "Agotado" : "Añadir al carrito"}
+      </Button>
+      <div className="mt-5 grid gap-3 rounded-2xl bg-slate-50 p-4 text-sm">
+        {outOfStock ? (
+          <span className="flex items-center gap-2 font-bold text-rose-600">
+            <XCircle className="size-4" />
+            Agotado
+          </span>
+        ) : lowStock !== null ? (
+          <span className="flex items-center gap-2 font-bold text-amber-600">
+            <TriangleAlert className="size-4" />
+            Quedan {lowStock} unidades
+          </span>
+        ) : (
+          <span className="flex items-center gap-2 font-bold">
+            <CheckCircle2 className="size-4 text-emerald-500" />
+            Disponibilidad por confirmar
+          </span>
+        )}
+        <span className="flex items-center gap-2 font-bold">
+          <Truck className="size-4 text-cyan-600" />
+          Envíos nacionales
+        </span>
+      </div>
+    </div>
+  );
 }