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/vendor/james-heinrich/phpthumb/demo/readme.demos.txt

@@ -0,0 +1,50 @@
+//////////////////////////////////////////////////////////////////
+//   phpThumb() by James Heinrich <info@silisoftware.com>       //
+//        available at http://phpthumb.sourceforge.net          //
+//             and/or https://github.com/JamesHeinrich/phpThumb //
+//////////////////////////////////////////////////////////////////
+///                                                             //
+//    phpThumb() included and related demos                     //
+//                                                             ///
+//////////////////////////////////////////////////////////////////
+
+The phpThumb() distribution includes several demos, and it
+should be self-evident what they do when you run them:
+
+* phpThumb.demo.check.php - configuration checker, will check
+    your config file and server configuration and warn of any
+    potential problems
+
+* phpThumb.demo.demo.php - shows a wide variety of samples,
+    basically all the different features and filters of phpThumb.
+    Note: sample image files are not included in the distribution
+    but can be downloaded from http://phpthumb.sourceforge.net/demo
+
+* phpThumb.demo.gallery.php - basic demonstration of a photo
+    gallery with ability to browse subdirectories. May use
+    phpThumb.demo.showpic.php for fullsize popup display
+
+* phpThumb.demo.showpic.php - auto-resizes a popup window to
+    match the dimensions of the image it is displaying
+
+* phpThumb.demo.object.php - example of how to call phpThumb
+    as an object.
+
+* phpThumb.demo.object.simple.php - simplified version of
+    phpThumb.demo.object.php with fewer options shown.
+
+* phpThumb.demo.random.php - select & display a random thumbnail
+    from a directory of images.
+
+
+
+Other people have created useful demos and/or extensions to
+phpThumb(). Some of these I know of are:
+(also see http://phpthumb.sourceforge.net for an updated list)
+
+* iManager/iBrowser        - http://www.j-cons.com/news/
+* ThumbnailSelector        - http://www.silisoftware.com/scripts/ThumbnailSelector
+* Applejuice Build_Gallery - http://twofivethreetwo.com/?nav=scripts
+
+If you know of any others you think should be mentioned here
+please let me know: info@silisoftware.com