feat: VivesPOS landing on Winter CMS 1.2 — theme + plugin + Dockerfile

- Base: wintercms/winter branch 1.2 (full framework)
- Theme vivespos: Canvas 7 + Bootstrap 5 CDN, custom CSS
- Layout: deferred GTM/GA4 tracking, JSON-LD SoftwareApplication
- Partials: hero (offline-first), features, modes (offline/nube toggle),
  screenshots, pricing (3 planes), comparison, FAQ, CTA
- Plugin VivesPOS.Site with ContactForm
- Dockerfile: PHP 8.2 Apache, port 80, healthcheck
- Added winter/wn-pages, blog, sitemap, seo plugins
- Active theme set to vivespos

modules/system/tests/plugins/database/NullableModelTest.php

@@ -0,0 +1,61 @@
+<?php
+
+namespace System\Tests\Plugins\Database;
+
+use System\Tests\Bootstrap\PluginTestCase;
+use Database\Tester\Models\NullablePost;
+
+class NullableModelTest extends PluginTestCase
+{
+    public function setUp() : void
+    {
+        parent::setUp();
+
+        include_once base_path() . '/modules/system/tests/fixtures/plugins/database/tester/models/Post.php';
+
+        $this->runPluginRefreshCommand('Database.Tester');
+    }
+
+    public function testNullifyingFields()
+    {
+        // Save as SQL default
+        $post = NullablePost::create(['author_nickname' => ''])->reload();
+        $this->assertEquals('Winter', $post->author_nickname);
+
+        // Save as empty string
+        $post->author_nickname = '';
+        $post->save();
+        $this->assertNull($post->author_nickname);
+    }
+
+    public function testNonEmptyValuesAreIgnored()
+    {
+        // Save as value
+        $post = NullablePost::create(['author_nickname' => 'Joe']);
+        $this->assertEquals('Joe', $post->author_nickname);
+
+        // Save as zero integer
+        $post->author_nickname = 0;
+        $post->save();
+        $this->assertNotNull($post->author_nickname);
+        $this->assertEquals(0, $post->author_nickname);
+
+        // Save as zero float
+        $post->author_nickname = 0.0;
+        $post->save();
+        $this->assertNotNull($post->author_nickname);
+        $this->assertEquals(0.0, $post->author_nickname);
+
+        // Save as zero string
+        $post->author_nickname = '0';
+        $post->save();
+        $this->assertNotNull($post->author_nickname);
+        $this->assertEquals('0', $post->author_nickname);
+
+        // Save as false
+        $post->author_nickname = false;
+        $post->save();
+        $this->assertNotNull($post->author_nickname);
+        $this->assertEquals(false, $post->author_nickname);
+    }
+}