docs: add Tests CI badge, features section, and crates.io metadata

[edisdev]

• README: add Tests workflow badge (test.yml) and Tauri v2 badge, split Build/Tests badges to their respective workflows
• README: add value proposition, Features, Testing, and Contributing sections
• Cargo.toml: add keywords, categories, and readme for crates.io discovery

Description

Related Issue

Fixes #

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📚 Documentation update
• 🔧 Refactoring (no functional changes)
• ✅ Test update

Platforms Tested

• Windows
• macOS
• Linux
• iOS
• Android

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Screenshots (if applicable)

Additional Notes