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/install/upgrade_v26.php

@@ -0,0 +1,47 @@
+<?php
+/**
+ * Database conversion script for DB v26
+ *
+ * Rating custom field conversion
+ *
+ * @package Setup
+ * @author  Andreas Goetz <cpuidle@gmx.net>
+ * @version $Id: upgrade_v26.php,v 1.2 2007/12/30 11:09:24 andig2 Exp $
+ */
+
+/**
+ * Rating data migration
+ */
+function migrate_rating($field)
+{
+    global $dbh;
+    
+    $set = runSQL('UPDATE videodata SET rating='.$field.' WHERE '.$field.'>0', $dbh, true);
+    return $set;
+}
+
+$sql    = "SELECT * FROM config WHERE opt LIKE 'custom%type'";
+$set	= runSQL($sql, $dbh, true);
+if ($set === false) return(false);
+
+foreach ($set as $row)
+{
+    if ($row['value'] == 'rating')
+    {
+        if (preg_match('/(custom\d)/', $row['opt'], $m))
+        {
+            $field = $m[1];
+            $set    = migrate_rating($field);
+            if ($set === false) return(false);
+            
+            $sql    = "UPDATE config SET value='' WHERE opt LIKE '".$field."%'";
+            $set    = runSQL($sql, $dbh, true);
+            if ($set === false) return(false);
+        }    
+    }
+}
+
+// signal success
+return true;
+
+?>