Add mod_custom hero layout override and bump version to 03.09.01

Adds src/html/mod_custom/hero.php — a banner-overlay style template
override for mod_custom, mirroring Cassiopeia's banner layout pattern.
Includes background image support via WebAssetManager and respects the
Module Manager's moduleclass_sfx field.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/html/mod_custom/hero.php

@@ -0,0 +1,36 @@
+<?php
+
+/**
+ * @package     Joomla.Site
+ * @subpackage  mod_custom
+ *
+ * @copyright   (C) 2026 Moko Consulting <hello@mokoconsulting.tech>
+ * @license     GNU General Public License version 2 or later; see LICENSE.txt
+ *
+ * Template override for mod_custom adding banner-overlay wrapper pattern.
+ * Based on Cassiopeia's banner layout approach.
+ */
+
+defined('_JEXEC') or die;
+
+use Joomla\CMS\HTML\HTMLHelper;
+use Joomla\CMS\Uri\Uri;
+
+$modId          = 'mod-custom' . $module->id;
+$moduleclass    = htmlspecialchars($params->get('moduleclass_sfx', ''), ENT_COMPAT, 'UTF-8');
+
+if ($params->get('backgroundimage')) {
+    /** @var Joomla\CMS\WebAsset\WebAssetManager $wa */
+    $wa = $app->getDocument()->getWebAssetManager();
+    $wa->addInlineStyle(
+        '#' . $modId . '{background-image: url("' . Uri::root(true) . '/' . HTMLHelper::_('cleanImageURL', $params->get('backgroundimage'))->url . '");}',
+        ['name' => $modId]
+    );
+}
+?>
+
+<div class="mod-custom custom banner-overlay<?php echo $moduleclass ? ' ' . $moduleclass : ''; ?>" id="<?php echo $modId; ?>">
+    <div class="overlay">
+        <?php echo $module->content; ?>
+    </div>
+</div>