Implemented the Structured Knowledge Persistence Pipeline

Implemented the Persistence Pipeline to safely and consistently store structured knowledge in the KnowledgeDB. Instead of persisting candidates generated by the Knowledge Structuring AI directly, the pipeline executes validation, decision making, schema transformation, save request construction, and persistence in separate stages, ensuring consistency across entities, relationships, and knowledge. This clear separation of responsibilities improves maintainability, extensibility, and reliability while providing a scalable foundation for future enhancements to the Knowledge Foundation.