feat: enhance payment status handling and summary in MyPaymentsPage

- Added support for 'partial' payment status in MyPaymentsPage and related components.
- Updated API responses to include 'paid_rials' and 'summary' for invoices.
- Introduced InvoicePaymentStatus service to derive payment status based on actual payments.
- Enhanced tests to cover new payment scenarios including partial payments and payment methods.
- Updated documentation to reflect changes in payment status and API responses.

src/Billing/Service/InvoicePaymentStatus.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace App\Billing\Service;
+
+/**
+ * وضعیت پرداخت یک صورتحساب.
+ *
+ * ستون `invoices.status` چرخه‌ی حیات صورتحساب را نگه می‌دارد (draft → finalized → void)
+ * و هرگز به `paid` نمی‌رود؛ پول واقعی در `session_payments` ثبت می‌شود. بنابراین وضعیت
+ * پرداخت **مشتق** است: مجموع پرداخت‌های مراجعه در برابر سهم بیمار (`patient_rials`).
+ * همین‌جا تنها مرجع این قاعده است تا نماها از هم واگرا نشوند.
+ */
+final class InvoicePaymentStatus
+{
+    public const PAID      = 'paid';
+    public const PARTIAL   = 'partial';
+    public const UNSETTLED = 'unsettled';
+
+    /** @return self::PAID|self::PARTIAL|self::UNSETTLED */
+    public static function resolve(int $dueRials, int $paidRials): string
+    {
+        if ($paidRials >= $dueRials) {
+            return self::PAID;
+        }
+
+        return $paidRials > 0 ? self::PARTIAL : self::UNSETTLED;
+    }
+}