- pets/[petId]/page.tsx: replace /api/avatar stub with NEXT_PUBLIC_R2_PUBLIC_URL CDN URL
- pets/[petId]/edit/page.tsx: pass initialAvatarKey to PetForm so AvatarUpload shows current photo
- Sidebar.tsx: add avatarKey to Pet type; show AvatarImage from CDN for active pet and dropdown list
- MobileNav.tsx: same CDN avatar pattern for mobile pet switcher
- next.config.ts: add images.remotePatterns for R2 CDN hostname (T-4-04 safeguard)