fix: Critical memory leak in TemplateLoader causing OOM errors

- Added recursion depth tracking to prevent infinite loops from shortcodes in content
- Nested items now skip the_content filter, using wp_kses_post() instead
- Made get_artist_data(), get_album_data(), get_track_data(), get_playlist_data() public
- Methods now accept both int post IDs and WP_Post objects
- Added $load_nested parameter to control nested item loading

Fixes memory exhaustion in Twig's StagingExtension when post content
contains FediStream shortcodes that trigger recursive template rendering.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

wp-fedistream.php

@@ -3,7 +3,7 @@
  * Plugin Name: WP FediStream
  * Plugin URI: https://src.bundespruefstelle.ch/magdev/wp-fedistream
  * Description: Stream music over ActivityPub - Build your own music streaming platform for Musicians and Labels.
- * Version: 0.4.0
+ * Version: 0.4.1
  * Requires at least: 6.4
  * Requires PHP: 8.3
  * Author: Marco Graetsch
@@ -26,7 +26,7 @@ if ( ! defined( 'ABSPATH' ) ) {
  *
  * @var string
  */
-define( 'WP_FEDISTREAM_VERSION', '0.4.0' );
+define( 'WP_FEDISTREAM_VERSION', '0.4.1' );
 
 /**
  * Plugin file path.