[UX] Transform the AZD UX style guide into AI skills

Improve the developer experience by transforming the AZD UX style guide from a static Markdown document into AI skills that provide contextual guidance during implementation.

This work includes:
* Understanding how the current Markdown-based UX style guide is consumed during development.
* Identifying scenarios where AI skills can provide more effective, contextual guidance than static documentation.
* Converting applicable UX guidance into reusable AI skills.
* Validating that the skills improve implementation quality and help developers apply UX best practices more consistently.