Task #19: Donation cart (سلة تبرعاتك) for EHSAN POC

Built a real donation cart matching ehsan.sa:
- CartContext provider (localStorage-persisted, defensive parsing) wired into App.tsx
- OpportunityCard: cart icon now adds the case with its typed amount and swaps the
  action row to an added state («مضاف لسلة تبرعاتك» + «إزالة»)
- Header cart button: live count badge + navigates to /cart
- New /cart page + route: breadcrumb, item list (delete icon, category, name,
  editable «قيمة المبلغ» amount, image+progress%), summary panel «الإجمالي» +
  green «للمتابعة للدفع», decorative leaf SVG background, empty state
- translations.ts: parallel AR+EN `cart` section
- donate.tsx: removes the donated case from the cart on successful donation
  (cart reconciliation), preventing stale added-state/badge

Notes/deviations:
- Checkout handoff routes the first cart item into the existing single-case donate
  flow (the POC backend has no multi-item payment). Reconciliation keeps remaining
  items coherent. A true multi-item checkout backend was out of scope.
- Verified with passing e2e test (add → badge → cart page → remove → empty) and
  clean tsc; architect review addressed (reconciliation + defensive parsing).

artifacts/ehsan-poc/src/lib/i18n/translations.ts

@@ -236,6 +236,19 @@ export const en = {
     paymentTitle: "Payment Details",
     selectAmountError: "Please select or enter a valid amount.",
   },
+  cart: {
+    title: "Your Donation Cart",
+    breadcrumbHome: "Home",
+    amountLabel: "Amount value",
+    remove: "Remove",
+    added: "Added to your donation cart",
+    addToCart: "Add to cart",
+    total: "Total",
+    proceedToPayment: "Proceed to Payment",
+    empty: "Your donation cart is empty",
+    emptyHint: "Browse the available opportunities and add the causes you wish to support.",
+    browse: "Browse Opportunities",
+  },
   admin: {
     title: "Admin Dashboard",
     caseId: "Case ID",
@@ -525,6 +538,19 @@ export const ar = {
     paymentTitle: "بيانات الدفع",
     selectAmountError: "الرجاء اختيار أو إدخال مبلغ صحيح.",
   },
+  cart: {
+    title: "سلة تبرعاتك",
+    breadcrumbHome: "الرئيسية",
+    amountLabel: "قيمة المبلغ",
+    remove: "إزالة",
+    added: "مضاف لسلة تبرعاتك",
+    addToCart: "أضف للسلة",
+    total: "الإجمالي",
+    proceedToPayment: "للمتابعة للدفع",
+    empty: "سلة تبرعاتك فارغة",
+    emptyHint: "تصفّح الفرص المتاحة وأضف القضايا التي ترغب بدعمها.",
+    browse: "تصفّح الفرص",
+  },
   admin: {
     title: "لوحة الإدارة",
     caseId: "رقم الحالة",