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/actors.tpl

@@ -0,0 +1,31 @@
+<div id="showcast">
+    <h3>{$lang.cast}:</h3>
+    <table width="100%">
+    {counter start=0 print=false name=castcount}
+    {foreach item=actor from=$video.cast}
+        {if $count == 0}
+        <tr>
+        {/if}
+            <td width="{floor(100/$config.castcolumns)}%">
+                {if $actor.imgurl}
+                    {assign var="link" value=$actor.imdburl}
+                    <a href="{if $config.imdbBrowser}{assign var="link" value=$link|escape:url}trace.php?videodburl={/if}{$link}">{html_image file=$actor.imgurl max_width=45 max_height=60 class=thumb}{*<img src="{$actor.imgurl}" width="38" height="52" align="left">*}</a>
+                {/if}
+                <a href="search.php?q=%22{$actor.name|escape:url}%22&amp;isname=Y">{$actor.name}</a>
+                {foreach item=role from=$actor.roles}
+                    <br/>{$role}
+                {/foreach}
+            </td>
+        {counter assign=count name=castcount}
+        {if $count == $config.castcolumns}
+        </tr>{counter start=0 print=false name=castcount}
+        {/if}
+    {/foreach}
+    {if $count != 0}
+        {section name="columnLoop" start=$count loop=$config.castcolumns}
+            <td>&nbsp;</td>
+        {/section}
+        </tr>
+    {/if}
+    </table>
+</div>