Per CommanderStorm's feedback, refactor the check() method into:
- checkKeyword() - for legacy keyword matching
- checkJsonQuery() - for legacy JSONata query
- checkConditions() - for new conditions system
Also add test cases for MQTT conditions:
- Message condition with contains operator
- Topic condition with equals operator
- Condition mismatch rejection
- Multiple conditions with AND logic
This improves readability and maintainability.