feat: add local video mode with media picker and install script

- New "Local Video" hero mode with Joomla Media Manager file picker
- Install script creates images/heroes/ folder on install/update
- Updated showMuteToggle to show for both video and localvideo modes
- All language strings (en-US/en-GB, ini + sys.ini) updated with new
  keys: MODE_LOCALVIDEO, LOCAL_VIDEO_LABEL/DESC, CARD_DELAY, MUTE_TOGGLE

Authored-by: Moko Consulting
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/script.php

@@ -0,0 +1,26 @@
+<?php
+
+/**
+ * @package     Joomla.Site
+ * @subpackage  mod_mokojoomhero
+ *
+ * @copyright   Copyright (C) 2026 Moko Consulting. All rights reserved.
+ * @license     GPL-3.0-or-later
+ */
+
+defined('_JEXEC') or die;
+
+use Joomla\CMS\Filesystem\Folder;
+use Joomla\CMS\Installer\InstallerAdapter;
+
+class Mod_MokojoomheroInstallerScript
+{
+    public function postflight(string $type, InstallerAdapter $adapter): void
+    {
+        $heroesPath = JPATH_ROOT . '/images/heroes';
+
+        if (!is_dir($heroesPath)) {
+            Folder::create($heroesPath);
+        }
+    }
+}