chore: release v5.4.0

- CHANGELOG.md: [Unreleased] → [5.4.0] - 2026-01-28
- README.md: title → v5.4.0
- marketplace.json: version → 5.4.0
- CLAUDE.md: version → 5.4.0

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

CHANGELOG.md

@@ -4,7 +4,7 @@ All notable changes to the Leo Claude Marketplace will be documented in this fil
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
-## [Unreleased]
+## [5.4.0] - 2026-01-28
 
 ### Added