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/core/VariableStream.class.php

@@ -0,0 +1,56 @@
+<?php
+/**
+ * VariableStream class
+ *
+ * @package Core
+ * @author  Andreas Goetz <cpuidle@gmx.de>
+ * @version $Id: VariableStream.class.php,v 1.4 2004/10/30 11:48:36 andig2 Exp $
+ */
+
+// stream wrappers require php > 4.3
+if (version_compare(phpversion(), '4.3') < 0)
+{
+    errorpage('PHP version mismatch', 
+              'At least PHP version 4.3.0 is required to run the VariableStream, please check the documentation!');
+}
+
+/**
+ * VariableStream allows XML reading from variables
+ * @package Core
+ */
+class VariableStream
+{
+    var $position;
+    var $varname;
+    var $context;
+    
+    function stream_open($path, $mode, $options, &$opened_path) {
+        $url = parse_url($path);
+        $this->varname = $url['host'];
+        $this->position = 0;
+        return true;
+    }
+    
+    function stream_read($count) {
+        $ret = substr($GLOBALS[$this->varname], $this->position, $count);
+        $this->position += strlen($ret);
+        return $ret;
+    }
+    
+    function stream_eof() {
+        return $this->position >= strlen($GLOBALS[$this->varname]);
+    }
+    
+    function stream_stat() {
+        return array('size' => strlen($GLOBALS[$this->varname]));
+    }  
+    
+    function url_stat() {
+        return array();
+    }
+}
+
+// register stream type to allow use in xml->load
+stream_wrapper_register('var', 'VariableStream');
+
+?>