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/Domain/Model/InvoiceLine.php

@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+namespace MiniShop\Invoicing\Domain\Model;
+
+final readonly class InvoiceLine
+{
+    public function __construct(
+        public string $description,
+        public int $quantity,
+        public int $unitPriceInCents,
+        public string $currency,
+        public TaxRate $taxRate,
+    ) {
+        if ($quantity <= 0) {
+            throw new \InvalidArgumentException('Quantity must be positive.');
+        }
+    }
+
+    public function lineTotalExclTax(): int
+    {
+        return $this->quantity * $this->unitPriceInCents;
+    }
+
+    public function lineTotalInclTax(): int
+    {
+        return (int) round($this->lineTotalExclTax() * (1 + $this->taxRate->rate));
+    }
+}