[feat] knowledge graph

[kakuka]

Description:
Integrate a built-in Product Manager knowledge graph into Icemark, covering key concepts, workflows, methodologies, and case studies. This graph will serve as an auxiliary knowledge source for the LLM, enabling it to produce more professional and context-aware outputs in tasks such as PRD generation, competitive analysis, and user research.

Goals:

Allow LLM to quickly access core PM knowledge

Improve the professionalism and reliability of generated content

Lay the foundation for future intelligent enhancement features