feat: bootstrap JOBcard CRM foundation

app/Domain/Jobcard/JobcardReference.php

@@ -0,0 +1,24 @@
+<?php
+declare(strict_types=1);
+
+namespace App\Domain\Jobcard;
+
+final class JobcardReference
+{
+    public static function generate(int $sequence, ?int $year = null): string
+    {
+        if ($sequence < 1) {
+            throw new \InvalidArgumentException('Sequence must be positive.');
+        }
+        $year ??= (int) date('Y');
+        if ($year < 2000 || $year > 9999) {
+            throw new \InvalidArgumentException('Year must be four digits.');
+        }
+        return sprintf('JC-%04d-%06d', $year, $sequence);
+    }
+
+    public static function isValid(string $reference): bool
+    {
+        return preg_match('/^JC-\d{4}-\d{6}$/', $reference) === 1;
+    }
+}