Comprehensive testing suite

[krjordan]

Implement full test coverage for production release.

Requirements

• Unit tests for all core modules
• Integration tests for MQTT functionality
• End-to-end CLI tests
• TUI component tests
• Error scenario testing
• Performance benchmarks

Acceptance Criteria

• >90% code coverage with unit tests
• All CLI commands have integration tests
• MQTT connection edge cases tested
• TUI components tested independently
• Performance regression tests
• CI runs all tests automatically