feat: restructure UX Patterns page and improve navigation

- Update footer to include new sub-pages (UX Patterns, Visual Patterns, Workflow & Rituals)
- Add darker background and backdrop effect to header submenu for better visibility
- Restructure UX Patterns page with proper section organization:
  - Interaction Patterns: Clean accordion with lighter styling
  - UI Kit: Dedicated section with proper header styling
  - Micro-interactions: Dedicated section with proper header styling
- Remove heavy frames from section content for cleaner appearance
- Simplify accordion design with lighter borders and hover effects
- Move UI Kit and Micro-interactions content to their own sections
- Apply consistent SectionTitle styling across all sections
- Improve mobile preview frame with proper 16:9 aspect ratio

All sections now follow the same styling pattern as Product Principles
with cleaner, more focused content presentation.

Author: mmaxence