feat: add platform homepage and content management system with improved UI

Implemented a comprehensive CMS for managing platform homepage and content pages:

- Platform homepage manager with template selection (default, minimal, modern)
- Content pages CRUD with platform defaults and vendor overrides
- Sidebar navigation for Content Management section
- Dedicated API endpoints for creating, updating, deleting pages
- Template support for customizable homepage layouts
- Header/footer navigation integration for content pages
- Comprehensive documentation for platform homepage setup
- Migration script for creating initial platform pages

UI improvements:
- Fixed action buttons styling in content pages table to match design system
- Added proper hover states, rounded corners, and better contrast
- Increased button size and padding for better usability

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

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

mkdocs.yml

@@ -21,6 +21,7 @@ nav:
       - Complete Setup Guide: getting-started/DATABASE_SETUP_GUIDE.md
       - Quick Reference: getting-started/DATABASE_QUICK_REFERENCE.md
     - CMS Quick Start: getting-started/cms-quick-start.md
+    - Platform Homepage Quick Start: getting-started/platform-homepage-quick-start.md
     - Configuration: getting-started/configuration.md
 
   # ============================================
@@ -149,6 +150,7 @@ nav:
     - Content Management System:
       - Overview: features/content-management-system.md
       - Implementation Guide: features/cms-implementation-guide.md
+    - Platform Homepage: features/platform-homepage.md
     - Vendor Landing Pages: features/vendor-landing-pages.md
 
   # ============================================