feat: add videodb media index with Docker stack

- Add videodb PHP/MySQL media collection manager (Blu-ray, DVD, CD)
- Dockerfile: PHP 8.1 + Apache with GD/mysqli/exif extensions
- docker-compose.yml: app on port 6761 + MySQL 8.0 with health checks
- docker-entrypoint.sh: auto-generates config.inc.php from env vars,
  waits for MySQL, initializes DB schema idempotently
- init-db.php: CLI schema installer using app's own prefix_query() logic
- Persistent volumes for DB, cache, and cover images

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

videodb/templates/modern/options_thumbs.tpl

@@ -0,0 +1,13 @@
+{*
+  Template to display thumbnails for available templates
+  $Id: options_thumbs.tpl,v 2.2 2006/11/11 16:18:13 andig2 Exp $
+*}
+
+<!-- {$smarty.template} -->
+
+{foreach item=thumb from=$option.thumbs}
+    <div class="setup-thumb">
+        <a href="{$smarty.server.PHP_SELF}?template={$thumb.name}&quicksave=1"><img src="{$thumb.img}"/><br/>
+        {$thumb.name}</a>
+    </div>
+{/foreach}