feat(docs): expand structured knowledge graph for Generative UI

[beginwebdev2002]

Standardized the frontend/design-ui directory into a machine-readable knowledge base. Added technical security/performance justification to the Solution block in frontend/design-ui/readme.md. Autonomously generated a new structural pattern module frontend/design-ui/generative-ui.md for AI-driven Generative UI following the mandatory Bad->Problem->Best->Solution cycle, including YAML frontmatter, deterministic emojis, Mermaid workflow diagram, and GitHub callouts. Updated index lists in both frontend/design-ui/readme.md and frontend/readme.md to establish the new module in the knowledge graph.

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PR created automatically by Jules for task 4842610354038209187 started by @beginwebdev2002

[google-labs-jules]

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