Docs: Update setup guides and add contribution guidelines

[secsovereign]

Description

Update development documentation to align with BitVault's architecture and establish consistent contribution guidelines

Changes

Setup Documentation

• Update Arch Linux setup guide to include BitVault-specific dependencies
• Add security-specific tools and testing requirements
• Update Makefile to remove Tauri and add security-focused targets

Contribution Guidelines

• Add standardized CONTRIBUTING.md in root directory
• Create detailed contribution guidelines with security focus
• Establish commit message conventions with imperative style
• Add professional CODE_OF_CONDUCT.md
• Implement branch naming conventions and PR templates

Security Considerations

These documentation updates emphasize security-first development practices and provide clear guidance on handling security-critical code, including:

• Process isolation and security boundary awareness
• Proper handling of sensitive information
• Security disclosure process
• Review requirements for security-critical changes

Testing

Documentation has been reviewed for:

• Consistency with project architecture
• Accuracy of setup instructions
• Clarity of contribution process
• Alignment with security principles

[secsovereign]

@jnowakowski @ilghan
Would you mind reviewing these changes to ensure they accurately represent our project's vision, security approach, and contribution process? Feedback welcome.

[jnowakowski]

LGTM, with a small nitpick: please rename makefile to Makefile to avoid potential confusion.