MS-257/feat: structure cleanup, navigation fixes, and mobile improvements

• Restore legal page links (CGV, Mentions légales, Politique de confidentialité)
• Remove newsletter
• Remove "Costumes" category
• Clean subcategories under "Chaussures et sacs/accessoires"
• Simplify "Beauté" category (Parfums, Maquillage, Soins/Accessoires only)
• Update liveuses image to banner format (remove side margins)
• Implement cookie consent
• Fix "Accéder au live" button behavior
• Fix footer links redirecting to top of page

Closes MS-257