Add shopping cart, store-items pages, contact form toast; skip workshops+portfolio

Neither workshops nor portfolio is in this tenant's enabledModules
(["products","blog","finance"]) - same reasoning as before, page/nav entry
withheld until either is actually enabled.

Shopping cart (new):
- CartProvider (client context): live cart state, add/update/remove/refresh,
  reads AUTH_TOKEN_COOKIE, calls the real /businesses/{id}/cart* endpoints
  (bearer-only, no guest cart - by design, not a gap)
- CartButton: header/bottom-nav icon with a live count badge and a popup
  preview; "ادامه" hands off to the customer portal's own cart/checkout,
  since this storefront has no checkout UI (address/payment) to hand off to
  internally - out of scope for this pass
- ProductBuyPanel: quantity stepper, wired to CartProvider.addItem() instead
  of its own ad-hoc fetch+token logic, toast on success
- Cart/CartItem types are a best-effort guess at an undocumented response
  shape (OpenAPI gives no field-level schema) - unverified against real data
  since store-items are still empty; read every field defensively

Store-items pages (new): /store-items (flat listing of purchasable variants,
always priced unlike /products) and /store-items/{id} (detail - no slug,
resolves the variant's productId and reuses the product's own gallery/
description/technical-info/comments/related-products, just with that
variant preselected).

Contact form: now shows a toast + inline success text and resets while
staying on screen, instead of swapping to a separate "thank you" panel.

New shared providers: ToastProvider (useToast) and CartProvider, both
mounted once in layout.tsx.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/components/Header.tsx

@@ -5,9 +5,9 @@ import Link from "next/link";
 import { useState } from "react";
 import SearchBox from "./SearchBox";
 import AccountMenu from "./AccountMenu";
-import { CartIcon, ChevronDown, GridIcon, PhoneIcon } from "./icons";
+import CartButton from "./CartButton";
+import { ChevronDown, GridIcon, PhoneIcon } from "./icons";
 import { MAIN_NAV, PHONE, PHONE_HREF, SITE_NAME } from "@/data/site";
-import { CUSTOMER_PORTAL_URL } from "@/lib/config";
 import { categoryHref } from "@/lib/slug";
 import type { AuthUser, CategoryNode } from "@/lib/types";
 
@@ -51,14 +51,10 @@ export default function Header({
 
           <div className="mr-auto hidden items-center gap-2 lg:flex">
             <AccountMenu user={user} />
-            <Link
-              href={`${CUSTOMER_PORTAL_URL}/cart`}
+            <CartButton
+              user={user}
               className="flex h-11 items-center gap-2 rounded-xl bg-brand px-3 text-[13px] text-white transition hover:bg-brand-dark"
-              aria-label="سبد خرید"
-            >
-              <CartIcon className="size-5" />
-              <span className="font-bold">۰</span>
-            </Link>
+            />
           </div>
         </div>