docs: add architecture rules and docs for e-commerce components

Architecture rules added:
- FE-008: Use number_stepper macro for quantity inputs
- FE-009: Use product_card macro for product displays
- FE-010: Use product_grid macro for product listings
- FE-011: Use add_to_cart macros for cart interactions
- FE-012: Use mini_cart macro for cart dropdown

Documentation:
- Update ui-components-quick-reference.md with e-commerce section
- Add component-standards.md for standardization guidelines
- Add ecommerce-components-proposal.md with full 20-component roadmap
- Update validate_architecture.py with FE-008 detection

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

mkdocs.yml

@@ -86,6 +86,7 @@ nav:
     - CDN Fallback Strategy: frontend/cdn-fallback-strategy.md
     - Tailwind CSS Build: frontend/tailwind-css.md
     - Shared Components:
+      - Component Standards: frontend/shared/component-standards.md
       - Jinja Macros Library: frontend/shared/jinja-macros.md
       - UI Components: frontend/shared/ui-components.md
       - UI Components Quick Reference: frontend/shared/ui-components-quick-reference.md
@@ -102,6 +103,7 @@ nav:
     - Shop Frontend:
       - Architecture: frontend/shop/architecture.md
       - Page Templates: frontend/shop/page-templates.md
+      - E-commerce Components Proposal: frontend/shop/ecommerce-components-proposal.md
       - Authentication Pages: frontend/shop/authentication-pages.md
       - Navigation Flow: frontend/shop/navigation-flow.md