feat(plans): 空库一键初始化默认套餐（带护栏与测试）

tests/Feature/AdminPlanSeedDefaultsTest.php

@@ -0,0 +1,58 @@
+<?php
+
+namespace Tests\Feature;
+
+use App\Models\Plan;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Tests\TestCase;
+
+class AdminPlanSeedDefaultsTest extends TestCase
+{
+    use RefreshDatabase;
+
+    protected function loginAsPlatformAdmin(): void
+    {
+        $this->seed();
+
+        $this->post('/admin/login', [
+            'email' => 'platform.admin@demo.local',
+            'password' => 'Platform@123456',
+        ])->assertRedirect('/admin');
+    }
+
+    public function test_platform_admin_can_seed_default_plans_when_empty(): void
+    {
+        $this->loginAsPlatformAdmin();
+
+        // 清空 seed 带来的默认套餐（测试口径：模拟空库）
+        Plan::query()->delete();
+        $this->assertSame(0, Plan::query()->count());
+
+        $this->post('/admin/plans/seed-defaults')
+            ->assertRedirect('/admin/plans');
+
+        $this->assertSame(2, Plan::query()->count());
+        $this->assertNotNull(Plan::query()->where('code', 'starter_monthly')->first());
+        $this->assertNotNull(Plan::query()->where('code', 'pro_yearly')->first());
+
+        $this->get('/admin/plans')
+            ->assertOk()
+            ->assertSee('基础版（月付）')
+            ->assertSee('专业版（年付）');
+    }
+
+    public function test_seed_default_plans_is_blocked_when_plans_exist(): void
+    {
+        $this->loginAsPlatformAdmin();
+
+        $this->assertTrue(Plan::query()->count() > 0);
+
+        $this->post('/admin/plans/seed-defaults')
+            ->assertRedirect();
+
+        // 不应新增到 2 条以上；且仍能打开列表
+        $this->get('/admin/plans')
+            ->assertOk()
+            ->assertSee('套餐管理');
+    }
+}