IAV-252/feat(agent): Link custom instructions to FAQ categories

Summary

Added optional association between custom instructions and FAQ categories to enable more granular instruction management.

Changes

• Added faqCategory field to AgentCustomInstruction entity
• Created lazy-loaded ManyToOne relationship with FaqCategory
• Added foreign key constraint fk_custom_instruction_faq_category

Notes

• Field is optional (nullable) to maintain backward compatibility
• Existing custom instructions will have null FAQ category by default

IAV-252