feat: Add plugin action links and user guide

- Add Settings and Dashboard links to the WordPress Plugins page
- Create comprehensive user guide (USERGUIDE.md) covering:
  - Installation and configuration
  - Managing artists, albums, tracks, and playlists
  - Shortcodes and widgets
  - ActivityPub and WooCommerce integration
  - User library features and troubleshooting

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

README.md

@@ -2,7 +2,7 @@
 
 Stream music over ActivityPub - Build your own music streaming platform for Musicians and Labels.
 
-[![Version](https://img.shields.io/badge/version-0.1.1-blue.svg)](CHANGELOG.md)
+[![Version](https://img.shields.io/badge/version-0.2.0-blue.svg)](CHANGELOG.md)
 [![PHP](https://img.shields.io/badge/PHP-%3E%3D8.3-purple.svg)](https://php.net)
 [![WordPress](https://img.shields.io/badge/WordPress-%3E%3D6.4-blue.svg)](https://wordpress.org)
 [![License](https://img.shields.io/badge/license-GPL--2.0%2B-green.svg)](https://www.gnu.org/licenses/gpl-2.0.html)