fix(ui): improve authentication UX and refine skin viewer components

- Add loading states to `ProfilePage` and `Navbar` to prevent flickering during authentication checks
- Implement animation pause/resume functionality in `SkinDetailModal` and `SkinViewer`
- Simplify `PageTransition` component by removing unnecessary complexity and state
- Refactor `SkinDetailModal` to use a more robust state management for animations
- Adjust `CharacterCard` skin dimensions for better layout consistency
- Clean up unused imports and redundant animation variants in several components

src/app/skins/page.tsx

@@ -3,8 +3,6 @@
 import { useState, useEffect, useCallback } from 'react';
 import { motion, AnimatePresence } from 'framer-motion';
 import { MagnifyingGlassIcon, EyeIcon, HeartIcon, ArrowDownTrayIcon, SparklesIcon, FunnelIcon, ArrowsUpDownIcon } from '@heroicons/react/24/outline';
-import { HeartIcon as HeartIconSolid } from '@heroicons/react/24/solid';
-import SkinViewer from '@/components/SkinViewer';
 import SkinDetailModal from '@/components/SkinDetailModal';
 import SkinCard from '@/components/SkinCard';
 import { searchTextures, toggleFavorite, type Texture } from '@/lib/api';