Step 00 — Squelette + intégration naïve

3 Bounded Contexts (Sales, Invoicing, LegacyFulfillment) avec :
- Domaines complets (agrégats, VOs, événements, invariants)
- Couche application (commands, queries, ports)
- Infrastructure in-memory (repos, gateway fake)
- Controllers HTTP Symfony
- Couplage naïf synchrone entre BC via NaiveSalesEventPublisher
- 20 tests unitaires et d'intégration passants

src/Invoicing/Infrastructure/Persistence/InMemoryInvoiceRepository.php

@@ -0,0 +1,37 @@
+<?php
+
+declare(strict_types=1);
+
+namespace MiniShop\Invoicing\Infrastructure\Persistence;
+
+use MiniShop\Invoicing\Application\Port\InvoiceRepository;
+use MiniShop\Invoicing\Domain\Model\Invoice;
+use MiniShop\Invoicing\Domain\Model\InvoiceId;
+
+final class InMemoryInvoiceRepository implements InvoiceRepository
+{
+    /** @var array<string, Invoice> */
+    private array $invoices = [];
+
+    public function save(Invoice $invoice): void
+    {
+        $this->invoices[$invoice->id->toString()] = $invoice;
+    }
+
+    public function get(InvoiceId $id): Invoice
+    {
+        return $this->invoices[$id->toString()]
+            ?? throw new \RuntimeException(sprintf('Invoice "%s" not found.', $id->toString()));
+    }
+
+    public function findByExternalOrderId(string $externalOrderId): ?Invoice
+    {
+        foreach ($this->invoices as $invoice) {
+            if ($invoice->externalOrderId === $externalOrderId) {
+                return $invoice;
+            }
+        }
+
+        return null;
+    }
+}