feat: add SendPaymentFailedReminderJob with grace guard

app/Jobs/SendPaymentFailedReminderJob.php

@@ -0,0 +1,44 @@
+<?php
+
+namespace App\Jobs;
+
+use App\Mail\PaymentFailedDay3Reminder;
+use App\Mail\PaymentFailedDay5Reminder;
+use App\Models\User;
+use Illuminate\Contracts\Queue\ShouldQueue;
+use Illuminate\Foundation\Queue\Queueable;
+use Illuminate\Support\Facades\Mail;
+use InvalidArgumentException;
+
+final class SendPaymentFailedReminderJob implements ShouldQueue
+{
+    use Queueable;
+
+    public function __construct(
+        public readonly int $userId,
+        public readonly int $day,
+    ) {
+        $this->onQueue('notifications');
+    }
+
+    public function handle(): void
+    {
+        $user = User::find($this->userId);
+
+        if ($user === null) {
+            return;
+        }
+
+        if ($user->grace_period_until === null) {
+            return;
+        }
+
+        $mailable = match ($this->day) {
+            3 => new PaymentFailedDay3Reminder($user),
+            5 => new PaymentFailedDay5Reminder($user),
+            default => throw new InvalidArgumentException("Unsupported reminder day: {$this->day}"),
+        };
+
+        Mail::to($user->email)->send($mailable);
+    }
+}