feat: Add Gitea Actions CI/CD pipeline for releases (v0.4.0)

- Automated release builds triggered by v* tags
- PHP 8.3 environment with production dependencies
- Automatic translation compilation (.po to .mo)
- Version verification (plugin version must match tag)
- WordPress-compliant zip structure
- SHA256 checksum generation
- Package structure verification
- Changelog extraction for release notes
- Automatic Gitea release creation with attachments

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: 0.3.0
+ * Version: 0.4.0
  * 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', '0.3.0' );
+define( 'WP_FEDISTREAM_VERSION', '0.4.0' );
 
 /**
  * Plugin file path.