feat: enhance GovStack token validation system with security improvements

[teefeh-07]

🚀 Enhancement Summary

This PR significantly improves the GovStack token validation smart contract with enhanced security, comprehensive testing, and better documentation.

🔧 Changes Made

Critical Fixes

• ✅ Fixed syntax error in contracts/real.clar (removed stray 'git' text)
• ✅ Enhanced contract validation logic with multiple security checks
• ✅ Added comprehensive error handling with specific error types

Security Improvements

• 🔒 Added principal format validation
• 🔒 Enhanced null/empty principal checks
• 🔒 Improved error specificity for better debugging
• 🔒 Added pre-validation assertions

New Features

• ✨ Added validate-principal read-only function
• ✨ Added get-validation-status read-only function
• ✨ Enhanced validation logic with multiple checks
• ✨ Added new error constants: ERR-UNAUTHORIZED and ERR-INVALID-PRINCIPAL

Testing Improvements

• 🧪 Complete test suite replacing placeholder tests
• 🧪 Comprehensive coverage for all contract functions
• 🧪 Error case testing scenarios
• 🧪 Read-only function validation tests
• 🧪 Edge case scenarios

Documentation & Configuration

• 📚 Updated README with detailed API reference
• 📚 Enhanced usage examples and security considerations
• 📚 Added project metadata in Clarinet.toml
• 📚 Improved testing documentation

🔍 Files Modified

• contracts/real.clar - Enhanced contract with security improvements
• tests/real_test.ts - Complete test suite implementation
• Clarinet.toml - Added project metadata and author information
• README.md - Enhanced documentation with detailed API reference

🧪 Testing

All tests have been thoroughly implemented and cover:

• ✅ Successful token validation scenarios
• ✅ Error handling for invalid inputs
• ✅ Read-only function behavior
• ✅ Edge cases and security scenarios

🔐 Security Considerations

This update significantly improves the security posture of the contract by:

• Adding multiple validation layers
• Implementing proper error handling
• Validating principal formats
• Preventing null/empty principal attacks

📋 Checklist

• Code follows project standards
• All tests pass
• Documentation updated
• Security considerations addressed
• No breaking changes to existing API
• Commit messages follow conventional format

🎯 Impact

This enhancement makes the GovStack token validation system more robust, secure, and production-ready while maintaining backward compatibility with existing integrations.