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/elegant/test.tpl

@@ -0,0 +1,27 @@
+{*
+  Template for testing data encoding
+*}
+
+<h3>Pre</h3>
+<div id="pre"><pre>{$data}</pre></div>
+
+<h3>Literal</h3>
+<div id="literal">{$data}</div>
+
+<h3>JS</h3>
+<div id="js"></div>
+
+<h3>HTML</h3>
+<div id="html">{$data|escape:html}</div>
+
+<h3>HTML all</h3>
+<div id="htmlall">{$data|escape:htmlall}</div>
+
+<h3>Alert</h3>
+<div>JS '<a href="#" onclick="javascript:alert('{$data|escape:javascript}')">Click here</a></div>
+<div>JS "<a href="#" onclick='javascript:alert("{$data|escape:javascript}")'>Click here</a></div>
+<div>JS & HTML <a href="#" onclick='javascript:alert("{$data|escape:javascript|escape}")'>Click here</a></div>
+
+<script language="JavaScript" type="text/javascript">
+	document.getElementById("js").innerHTML = '{$data|escape:javascript}';
+</script>