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/metal.css

@@ -0,0 +1,98 @@
+body      {font-family:sans-serif;font-size:16px; background-image:url(metal/alu.jpg);}
+
+
+
+input,textarea,select,option {background-color:#C7C7D1; background-image:url(metal/alu.jpg);}
+
+
+
+a:link    {text-decoration:none; color:#333366;}
+
+a:visited {text-decoration:none; color:#333366;}
+
+a:active  {text-decoration:none; color:#333366;}
+
+a:hover   {text-decoration:none; color:#333399;}
+
+
+
+.even {background-image:url(metal/alu3.jpg);}
+
+.odd  {background-image:url(metal/alu2.jpg);}
+
+.lent {background-image:url(metal/alu4.jpg);}
+
+
+
+.center {text-align: center;}
+
+
+
+.filter {font-size:12px}
+
+
+
+.list_title {font-weight:bold}
+
+.list_diskid {font-weight:bold;font-size:12px}
+
+.list_seen {font-size:12px}
+
+.list_info {font-style:italic}
+
+.list_plot {font-size:12px}
+
+
+
+.tableborder {border-width:1px;
+
+              border-style:solid;
+
+              border-left-color:#ffffff;
+
+              border-right-color:#555555;
+
+              border-top-color:#ffffff;
+
+              border-bottom-color:#555555;}
+
+.infobox {    border-width:1px;
+
+              border-style:solid;
+
+              border-left-color:#ffffff;
+
+              border-right-color:#555555;
+
+              border-top-color:#ffffff;
+
+              border-bottom-color:#555555; font-size:18px;
+
+              text-align:center;}
+
+.infobox td {text-align:center}
+
+.toplink {    padding:2px;
+
+              background-image:url(metal/alu3.jpg);
+
+              border-width:1px;
+
+              border-style:solid;
+
+              border-left-color:#ffffff;
+
+              border-right-color:#555555;
+
+              border-top-color:#ffffff;
+
+              border-bottom-color:#555555;}
+
+.splitbrain { font-size:10px;}
+
+.version {    font-size:10px;
+
+              border-width:1px;
+
+              border-style:solid;
+