Fix discount calculation: مصاريف تنمية excluded from discountable base

Business rule: the 35 EGP development fee is a flat non-discountable surcharge
added AFTER all discounts are applied. Discount applies only to base_amount.

Correct formula: discount = base × pct, total = (base - discount) + dev_fee
Previous (wrong): discount = (base + dev_fee) × pct

For member 51 (2023/2024): 410×50% = 205 discount, total = 205 + 35 = 240
(was incorrectly: 445×50% = 222.50, total = 222.50)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/Modules/Subscriptions/Services/SubscriptionGenerator.php

@@ -73,10 +73,9 @@ final class SubscriptionGenerator
             );
             if ($existing) { $skipped++; continue; }
 
-            // Member subscription
-            $gross = bcadd($memberRate, $devFee, 2);
-            $discount = $discountPct ? bcdiv(bcmul($gross, $discountPct, 4), '100', 2) : '0.00';
-            $total = bcsub($gross, $discount, 2);
+            // Member subscription — discount on base only, dev fee added after
+            $discount = $discountPct ? bcdiv(bcmul($memberRate, $discountPct, 4), '100', 2) : '0.00';
+            $total = bcadd(bcsub($memberRate, $discount, 2), $devFee, 2);
             $db->insert('subscriptions', [
                 'member_id'       => $memberId,
                 'financial_year'  => $financialYear,

database/migrations/Phase_92_003_fix_discount_excludes_dev_fee.php

+<?php
+declare(strict_types=1);
+
+/**
+ * Fix 2023/2024 discount calculation: مصاريف تنمية (35 EGP) must NOT be
+ * included in the discountable base. Discount applies only to base_amount,
+ * then dev fee is added as a flat non-discountable surcharge.
+ *
+ * Correct formula: discount = base_amount × 50%, total = base_amount - discount + dev_fee
+ */
+return function (\App\Core\Database $db): void {
+    $rows = $db->select(
+        "SELECT id, base_amount, development_fee
+         FROM subscriptions
+         WHERE financial_year = '2023/2024' AND status IN ('pending', 'overdue')"
+    );
+
+    foreach ($rows as $row) {
+        $discount = bcdiv($row['base_amount'], '2', 2); // 50% of base only
+        $newTotal = bcadd(bcsub($row['base_amount'], $discount, 2), $row['development_fee'], 2);
+
+        $db->query(
+            "UPDATE subscriptions SET discount_amount = ?, total_amount = ?, updated_at = NOW() WHERE id = ?",
+            [$discount, $newTotal, (int) $row['id']]
+        );
+    }
+};