Bill transfer storage monthly with a 15-day grace period before deletion.

Files stay available while wallet renewals succeed each month. Failed renewals
keep files for TRANSFER_GRACE_PERIOD_DAYS (default 15) before automatic cleanup.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/Feature/TransferTest.php

@@ -8,15 +8,18 @@ use Illuminate\Foundation\Testing\RefreshDatabase;
 use Illuminate\Http\UploadedFile;
 use Illuminate\Support\Facades\Storage;
 use Illuminate\Support\Str;
+use Tests\Concerns\FakesTransferBilling;
 use Tests\TestCase;
 
 class TransferTest extends TestCase
 {
+    use FakesTransferBilling;
     use RefreshDatabase;
 
     public function test_authenticated_user_can_create_transfer_with_files(): void
     {
         Storage::fake('qr');
+        $this->fakeTransferBillingApi();
 
         $user = User::create([
             'public_id' => (string) Str::uuid(),
@@ -27,7 +30,6 @@ class TransferTest extends TestCase
         $response = $this->actingAs($user)->post(route('transfer.transfers.store'), [
             'title' => 'Project assets',
             'message' => 'Here are the files.',
-            'retention_days' => 14,
             'files' => [
                 UploadedFile::fake()->create('brief.pdf', 100, 'application/pdf'),
                 UploadedFile::fake()->create('photo.jpg', 50, 'image/jpeg'),
@@ -41,7 +43,8 @@ class TransferTest extends TestCase
 
         $transfer = Transfer::first();
         $this->assertNotNull($transfer->qr_code_id);
-        $this->assertSame(14, $transfer->retention_days);
+        $this->assertNotNull($transfer->paid_until);
+        $this->assertTrue($transfer->paid_until->isFuture());
     }
 
     public function test_dashboard_requires_auth(): void