Bootstrap Kafka source connector with factory support and position validation

[qodo-code-review]

Description

• Extend KurrentDB connectors framework to support source connectors alongside existing sink connectors
• Implement Kafka source connector registration and factory instantiation
• Prevent users from starting or resetting source connectors from a specific position, as sources manage their own position tracking

Deliverables

• Catalogue Registration: Register KafkaSource connector with validator and data protector in ConnectorCatalogue
• Factory Support: Implement SystemConnectorsFactory to create and configure source connector instances with processor
• Data Protection: Add KafkaSourceConnectorDataProtector to protect sensitive Kafka source configuration
• Position Validation: Add domain validation to prevent StartConnector and ResetConnector commands from specifying start positions for source connectors

[linear]

DB-1773