perf(db): composite index on wallet_transactions(user_id, type) (M14)

Helps the per-type SUM balance query. M13 (service_items.section_id) and M15
(clinic_doctor_invitations.doctor_id) were false positives — both columns carry
a FK and are therefore auto-indexed by InnoDB; verified against the live schema.

Structural regression: InfraSmokeTest::testWalletUserTypeIndexExists.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/audit-backlog.md

@@ -66,9 +66,9 @@ _None outstanding._
 | M10 | Unbounded list: `listMine` settlements `findByUser` no limit | src/Settlement/Controller/SettlementController.php:193 | perf-pagination | GET settlement list → paginate |
 | M11 | Unbounded list: admin `pendingComments` `findPending` no limit | src/Rating/Controller/RatingController.php:350 | perf-pagination | admin moderation large backlog → paginate |
 | M12 | Unbounded list: public `listComments` per-doctor no limit | src/Rating/Controller/RatingController.php:270 | perf-pagination | popular doctor comments → paginate |
-| M13 | Missing index: `ServiceItem.section_id` FK fully unindexed (entity has zero indexes) | src/ClinicService/Entity/ServiceItem.php:23-24 | perf-index | EXPLAIN findBySection → no full scan |
-| M14 | Missing index: `WalletTransaction(user_id, type)` composite for per-type SUM | src/Settlement/Entity/WalletTransaction.php:38-39 | perf-index | EXPLAIN balance SUM query |
-| M15 | Missing index: `ClinicDoctorInvitation.doctor_id` FK unindexed | src/ClinicInvitation/Entity/ClinicDoctorInvitation.php:41-42 | perf-index | EXPLAIN findPendingByDoctor |
+| ⚠️M13 | Missing index: `ServiceItem.section_id` FK fully unindexed (entity has zero indexes) | src/ClinicService/Entity/ServiceItem.php:23-24 | perf-index | EXPLAIN findBySection → no full scan |
+| ✅M14 | Missing index: `WalletTransaction(user_id, type)` composite for per-type SUM | src/Settlement/Entity/WalletTransaction.php:38-39 | perf-index | **DONE** — added composite `idx_wallet_user_type` + migration. `InfraSmokeTest::testWalletUserTypeIndexExists`. |
+| ⚠️M15 | Missing index: `ClinicDoctorInvitation.doctor_id` FK unindexed | src/ClinicInvitation/Entity/ClinicDoctorInvitation.php:41-42 | perf-index | **FALSE POSITIVE** — `doctor_id` has a FK → auto-indexed (IDX_26DCCFEB87F4FB17 exists). No change. |
 | M16 | `User.email` and `User.nationalCode` not unique → duplicate identities | src/Auth/Entity/User.php:31-32,37-38 | db-unique | Insert two users same email/national_code → 2nd rejected. ⚠️ check dup data first |
 | M17 | `Payment.gatewayToken` not unique | src/Payment/Entity/Payment.php:58-59 | db-unique | Two payments same gateway_token → rejected |
 | M18 | `DateOverride` no UNIQUE `(doctor_id, date)` → ambiguous schedule | src/Appointment/Entity/DateOverride.php:12 | db-unique | Two overrides same doctor+date → rejected |

migrations/Version20260628165710.php

@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DoctrineMigrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+/**
+ * Auto-generated Migration: Please modify to your needs!
+ */
+final class Version20260628165710 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return '';
+    }
+
+    public function up(Schema $schema): void
+    {
+        // this up() migration is auto-generated, please modify it to your needs
+        $this->addSql('CREATE INDEX idx_wallet_user_type ON wallet_transactions (user_id, type)');
+    }
+
+    public function down(Schema $schema): void
+    {
+        // this down() migration is auto-generated, please modify it to your needs
+        $this->addSql('DROP INDEX idx_wallet_user_type ON wallet_transactions');
+    }
+}

src/Settlement/Entity/WalletTransaction.php

@@ -11,6 +11,7 @@ use Symfony\Component\Uid\Uuid;
 #[ORM\Entity(repositoryClass: WalletTransactionRepository::class)]
 #[ORM\Table(name: 'wallet_transactions')]
 #[ORM\Index(columns: ['user_id', 'created_at'], name: 'idx_wallet_user_date')]
+#[ORM\Index(columns: ['user_id', 'type'], name: 'idx_wallet_user_type')]
 class WalletTransaction
 {
     public const TYPE_CREDIT = 'credit';

tests/Smoke/InfraSmokeTest.php

@@ -31,4 +31,16 @@ class InfraSmokeTest extends ApiTestCase
         $this->assertTrue($body['success']);
         $this->assertSame($user->getUuid(), $body['data']['uuid']);
     }
+
+    public function testWalletUserTypeIndexExists(): void
+    {
+        $conn  = $this->em->getConnection();
+        $count = (int) $conn->fetchOne(
+            "SELECT COUNT(*) FROM information_schema.STATISTICS
+              WHERE TABLE_SCHEMA = DATABASE()
+                AND TABLE_NAME = 'wallet_transactions'
+                AND INDEX_NAME = 'idx_wallet_user_type'"
+        );
+        $this->assertGreaterThan(0, $count, 'composite index idx_wallet_user_type is missing');
+    }
 }