feat(tools): Automate Balena Etcher installation

## Description
Add an automated installation script for Balena Etcher to follow the "spilled coffee" principle - making it easy to set up a fully operational environment quickly.

## Proposed Solution
Create a script in `utils/install-balena-etcher.sh` that:

1. Downloads the latest portable version of Balena Etcher from GitHub releases
2. Extracts it to an appropriate location (e.g., `~/ppv/tools/balena-etcher/`)
3. Creates a desktop entry file in `~/.local/share/applications/`
4. Makes the application executable
5. Updates the desktop database

## Implementation Details
- Use GitHub API to fetch the latest release information
- Download the Linux x64 zip file
- Extract to a consistent location
- Create desktop entry with proper paths
- Follow the same pattern as other installation scripts (e.g., `install-go.sh`)
- Include detection for existing installations to avoid duplicates
- Add proper error handling and user feedback

## Benefits
- Consistent with dotfiles philosophy of automation
- Follows "spilled coffee" principle for quick setup
- Avoids dependency issues with older .deb packages
- Ensures users always get the latest version

## Additional Notes
- Should detect OS and architecture to download appropriate version
- Consider adding to the main setup.sh script as an optional tool
- Document the installation process in README.md

Start by comparing the proposed utils/install-balena-etcher.sh with install-go.sh, then review setup.sh and README.md for integration points. Verify the GitHub release lookup, Linux x64 download and extraction paths, desktop entry creation, executable permissions, desktop database update, and existing-installation handling. Done means the script installs the latest supported Etcher without duplicates and provides appropriate feedback.

Written by the indexing model from the issue text.