fix(models): correct UserSetting import namespace and add test coverage

tests/Unit/Models/UserSettingTest.php

@@ -0,0 +1,34 @@
+<?php
+
+namespace Tests\Unit\Models;
+
+use App\Features\Settings\Models\UserSetting;
+use App\Models\User;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use PHPUnit\Framework\Attributes\Test;
+use Tests\TestCase;
+
+class UserSettingTest extends TestCase
+{
+    use RefreshDatabase;
+
+    #[Test]
+    public function it_belongs_to_a_user(): void
+    {
+        $setting = UserSetting::factory()->create();
+
+        $this->assertInstanceOf(User::class, $setting->user);
+    }
+
+    #[Test]
+    public function it_has_fillable_attributes(): void
+    {
+        $setting = new UserSetting();
+
+        $this->assertEquals([
+            'user_id',
+            'setting_key',
+            'setting_value',
+        ], $setting->getFillable());
+    }
+}