docs: mark header component task as complete in TODO.md

Author: nullcoder

docs/TODO.md

@@ -100,7 +100,7 @@ This document tracks the implementation progress of GhostPaste. Check off tasks
 
 ### Layout Components
 
-- [ ] Create Header component with navigation - [#53](https://github.com/nullcoder/ghostpaste/issues/53)
+- [x] Create Header component with navigation - [#53](https://github.com/nullcoder/ghostpaste/issues/53)
 - [ ] Create Footer component - [#70](https://github.com/nullcoder/ghostpaste/issues/70)
 - [ ] Create Container component for consistent spacing - [#62](https://github.com/nullcoder/ghostpaste/issues/62)
 - [x] Implement responsive design tokens - [#57](https://github.com/nullcoder/ghostpaste/issues/57)