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/login.tpl

@@ -0,0 +1,34 @@
+{*
+  Output of login page
+*}
+
+
+<div align="center">
+  <p>{$lang.enterusername}</p>
+
+  <form action="login.php" id="login" method="post">
+  <input type="hidden" value="{$refer}" name="refer"/>
+  <table class="tableborder">
+    <tr>
+      <td>{$lang.username}:</td>
+      <td><input type="textbox" id="username" name="username"/></td>
+    </tr>
+    <tr>
+      <td>{$lang.password}:</td>
+      <td><input type="password" name="password"/></td>
+    </tr>
+    <tr>
+      <td colspan="2"><input type="checkbox" name="permanent" id="permanent" value="1"/><label for="permanent">{$lang.stayloggedin}</label></td>
+    </tr>
+    <tr>
+      <td colspan="2" align="middle" style="text-align:center"><input type="submit" value="{$lang.login}"/></td>
+    </tr>
+  </table>
+  </form>
+
+  <p>{$error}</p>
+</div>
+
+<script language="JavaScript" type="text/javascript">
+	document.forms['login'].username.focus();
+</script>