chore: upgrade to v0.2.0 with comprehensive improvements

[lzjever]

v0.2.0 Release

This PR upgrades atloop to v0.2.0 with comprehensive code quality, performance, and infrastructure improvements.

🎯 Key Improvements

Performance

• ✅ Memory formatting cache with automatic invalidation (expected hit rate > 80%)
• ✅ Performance benchmarks for memory formatting
• ✅ Performance profiling tools

Code Quality

• ✅ Fixed all 79 ruff violations (zero code quality issues)
• ✅ Replaced all broad exception handling with specific types
• ✅ Enhanced type checking configuration
• ✅ Added PEP 561 type marker (py.typed)
• ✅ Pre-commit hooks for automated code quality checks

Testing & Reliability

• ✅ Enforced 60% minimum test coverage threshold
• ✅ Fixed all test failures
• ✅ 547 tests passing

Security & Maintenance

• ✅ Security scanning workflow (pip-audit + bandit)
• ✅ Dependabot configuration for automated dependency updates
• ✅ Error metrics collection for monitoring

Documentation

• ✅ Updated CHANGELOG with v0.2.0 release notes
• ✅ Comprehensive improvement documentation

📊 Statistics

• Files changed: 51
• Insertions: +3,174
• Deletions: -910
• Tests: 547 passing
• Code quality: 0 violations

✅ Verification

• All tests passing
• All code quality checks passing
• All ruff checks passing
• Coverage threshold met

📝 Related Documentation

• CODE_REVIEW_AND_IMPROVEMENT_PLAN.md - Full review and improvement plan
• IMPROVEMENTS_SUMMARY.md - Summary of all improvements
• IMPROVEMENTS_PHASE1_COMPLETE.md - Phase 1 completion report
• IMPROVEMENTS_PHASE2_COMPLETE.md - Phase 2 completion report
• IMPROVEMENTS_PHASE3_COMPLETE.md - Phase 3 completion report