Bump version to 4.0.1 with Web UI improvements

- Update version to 4.0.1 across constants.py, __init__.py, pyproject.toml, README
- Refactor channel key UI from radio buttons to select dropdown
- Add LED indicator and key capsule CSS styles
- Reorganize encode/decode forms: RSA key section moved up, PIN + Channel in row
- Streamline channel key JavaScript for dropdown-based selection

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

README.md

@@ -5,7 +5,7 @@ A secure steganography system for hiding encrypted messages in images using hybr
 ![Python](https://img.shields.io/badge/Python-3.10--3.12-blue)
 ![License](https://img.shields.io/badge/License-MIT-green)
 ![Security](https://img.shields.io/badge/Security-AES--256--GCM-red)
-![Version](https://img.shields.io/badge/Version-4.0.0-purple)
+![Version](https://img.shields.io/badge/Version-4.0.1-purple)
 
 ## Features