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/nexgen/contrib.tpl

@@ -0,0 +1,17 @@
+{*
+  Tools template
+  $Id: contrib.tpl,v 1.3 2013/03/12 19:13:18 andig2 Exp $
+*}
+<!-- {$smarty.template} -->
+<div class="row">
+	<div class="small-12 large-10 columns small-centered">
+		<h3 class="subheader">{$lang.contrib}</h3>
+		<div class="small-cols-1 large-cols-2">
+			<ul class="six side-nav">
+				{foreach item=file from=$files}
+				<li><a href="{$file[0]}">{$file[1]}</a></li>
+				{/foreach}
+			</ul>
+		</div><!-- two-col -->
+	</div><!-- col -->
+</div><!-- row -->