Add ability for users to donate to multiple items in their cart at once

Implement multi-item donation checkout flow, including form validation, error handling for partial failures, and success messaging.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 1fa9329f-0cec-4a2f-80e8-e26dbae3142e
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Event-Id: 2339a9db-a182-40b6-a165-d906737c84f7
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/4d696b13-86f2-4c9d-be0d-95b293430047/1fa9329f-0cec-4a2f-80e8-e26dbae3142e/ZkqO90V
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artifacts/ehsan-poc/src/lib/i18n/translations.ts

@@ -344,6 +344,9 @@ export const en = {
     empty: "Your donation cart is empty",
     emptyHint: "Browse the available opportunities and add the causes you wish to support.",
     browse: "Browse Opportunities",
+    amountRequired: "Please enter an amount for each item in the cart.",
+    itemsCount: "Items",
+    successMessage: "Thank you. Your donations have been completed successfully. May Allah reward you.",
   },
   admin: {
     title: "Admin Dashboard",
@@ -742,6 +745,9 @@ export const ar = {
     empty: "سلة تبرعاتك فارغة",
     emptyHint: "تصفّح الفرص المتاحة وأضف القضايا التي ترغب بدعمها.",
     browse: "تصفّح الفرص",
+    amountRequired: "الرجاء إدخال قيمة المبلغ لكل عنصر في السلة.",
+    itemsCount: "عدد العناصر",
+    successMessage: "شكراً لك. تمت تبرعاتك بنجاح. جزاك الله خيراً.",
   },
   admin: {
     title: "لوحة الإدارة",