Bump version to 0.4.0

- Add CHANGELOG entry for self-licensing prevention feature
- Update plugin header and constant to 0.4.0

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

CHANGELOG.md

@@ -7,6 +7,25 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.4.0] - 2026-01-24
+
+### Added
+
+- Self-licensing prevention: Plugin automatically bypasses license validation when the configured license server URL points to the same WordPress installation
+- New `isSelfLicensing()` method in `PluginLicenseChecker` to detect circular licensing scenarios
+- New `normalizeDomain()` helper method for domain comparison (strips www prefix, lowercases)
+
+### Changed
+
+- `isLicenseValid()` and `validateLicense()` now check for self-licensing before attempting validation
+- Cache clearing now also clears the self-licensing check cache
+
+### Technical Details
+
+- Self-licensing detection compares normalized domains of license server URL and current site URL
+- Prevents circular dependency where plugin would try to validate against itself
+- Plugins can only be validated against the original store from which they were obtained
+
 ## [0.3.9] - 2026-01-24
 
 ### Added