Add comprehensive Bluefin Administrator's Guide with proper grammar and copyediting

[Copilot]

This PR addresses the issue of creating and copyediting the administration.md file by adding a comprehensive Administrator's Guide for Bluefin.

What was added

The new administration.md file provides a complete reference for system administrators managing Bluefin deployments, including:

• System Overview: Architecture and key components explanation
• Installation and Setup: Requirements, installation steps, and post-installation configuration
• System Management: Essential ujust commands and system updates via bootc
• Package Management: Homebrew for CLI tools and Flatpak for desktop applications
• Security Configuration: Secure Boot setup and firewall management
• Networking: Tailscale integration and NetworkManager usage
• Troubleshooting: System recovery, log analysis, and common issue resolution
• Maintenance and Updates: Automatic update management and system health monitoring
• Community and Support: Links to documentation, forums, and support resources

Grammar and copyediting improvements

The document has been carefully reviewed for:

• Clear, professional language throughout
• Consistent terminology and style
• Proper markdown formatting
• Comprehensive table of contents
• Quick reference section for common commands
• All content validated with pre-commit hooks

Integration with existing documentation

The guide references the existing tip that mentions the "Bluefin Administrator's Guide" at docs.projectbluefin.io/administration, providing the comprehensive technical information promised to users. It includes all the key features mentioned in the system tips, such as ujust commands, bootc rollback functionality, brew package management, and Tailscale integration.

This addition completes the documentation ecosystem by providing administrators with the in-depth technical guidance needed to effectively manage Bluefin systems.

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