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/default/trace.tpl

@@ -0,0 +1,26 @@
+{*
+
+  Template for browsing IMDB through VideoDB
+
+  $Id: trace.tpl,v 2.10 2005/05/20 10:02:17 andig2 Exp $
+
+*}
+
+
+
+<table width="100%" class="tableborder">
+
+  <tr>
+
+    <td>URL: </span><a href="{$url}" target="_blank">{$url}</a></td>
+
+    <td nowrap="nowrap" align="right" style="text-align:right">{if $fetchtime}{$lang.fetchtime}: {$fetchtime}s{/if}
+
+    <td align="right" style="text-align:right;">
+
+      <form action="trace.php" method="get" style="margin:0px; padding:0px;">
+
+        <input type="hidden" name="videodburl" value="{$url}" />
+
+        <input type="hidden" name="videodbreload" value="Y" />
+