feat: full UI redesign with design system, Nielsen heuristics compliance

- Install lucide-react, framer-motion, react-hot-toast, clsx, tailwind-merge
- Custom Tailwind config: semantic color tokens, Inter font, shadow scale,
  border radius scale, custom animations (fadeIn, slideUp, shimmer)
- Shared component library: Button, Badge, Card, Input, Select, Textarea,
  EmptyState, Skeleton, LoadingSpinner
- Global CSS with @layer components (.btn, .card, .input, .badge, .skeleton)
- Toast notification system via react-hot-toast + showToast utility
- ErrorBoundary wrapper for graceful error recovery
- Redesigned navigation: sticky, active state indicators, Lucide icons
- Dashboard: hero header, today highlighting, scrollable week grid,
  redesigned meal cards, empty states, skeleton loading
- Meal Detail: hero image with gradient overlay, metadata row with icons,
  Lucide star rating, edit-existing-feedback flow
- Pantry: inline add form, search/filter, visual quantity badges,
  expiry warnings, confirmation dialogs
- Shopping List: gradient summary cards, aisle grouping with badges,
  sale strikethrough pricing, empty state
- Login: centered card with icon, Input component, Button component
- All old gray/blue utility classes migrated to new surface/primary tokens
- TypeScript clean, production build passes

frontend/package.json

@@ -10,21 +10,26 @@
     "lint": "eslint . --ext ts,tsx --report-unused-disable-directives --max-warnings 0"
   },
   "dependencies": {
+    "@tanstack/react-query": "^5.17.0",
+    "axios": "^1.6.5",
+    "clsx": "^2.1.1",
+    "framer-motion": "^12.38.0",
+    "lucide-react": "^1.16.0",
     "react": "^18.2.0",
     "react-dom": "^18.2.0",
+    "react-hot-toast": "^2.6.0",
     "react-router-dom": "^6.21.1",
-    "@tanstack/react-query": "^5.17.0",
-    "axios": "^1.6.5"
+    "tailwind-merge": "^3.6.0"
   },
   "devDependencies": {
     "@types/react": "^18.2.48",
     "@types/react-dom": "^18.2.18",
     "@vitejs/plugin-react": "^4.2.1",
     "autoprefixer": "^10.4.16",
+    "eslint": "^8.56.0",
     "postcss": "^8.4.33",
     "tailwindcss": "^3.4.1",
     "typescript": "^5.3.3",
-    "vite": "^5.0.11",
-    "eslint": "^8.56.0"
+    "vite": "^5.0.11"
   }
 }