Add TelegramCommandHandler class with long polling, command routing,
and security features.
Changes:
- Add TelegramCommandHandler class to telegram_client.py
- Implement long polling with getUpdates API
- Add command registration and routing mechanism
- Implement chat ID verification for security
- Add comprehensive tests (16 tests)
- Coverage: 85% for telegram_client.py
Features:
- start_polling() / stop_polling() lifecycle management
- register_command() for handler registration
- Chat ID verification to prevent unauthorized access
- Error isolation (command failures don't crash system)
- Graceful handling of API errors and timeouts
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
