feat: add core PWA screens (auth, dashboard, purchases, products, alerts, settings)

Build all 8 primary screens for CAR-33 on top of the Phase 1 scaffold:
- Auth: login, register, forgot password with JWT flow and mock fallback
- Dashboard: triggered alerts banner, spending stats, price trend sparklines (Recharts), recent purchases
- Purchase History: store filter chips, paginated list with item previews
- Purchase Detail: receipt view with line items linking to product pages
- Products: search with instant filter, store price comparison badges
- Product Detail: 90-day price history chart (Recharts), store comparison table
- Store Comparison: ranked store cards with savings banner
- Price Alerts: triggered/watching sections, create form, progress bars, delete
- Coupons: expiration warnings, copy-to-clipboard coupon codes
- Account Linking: connect Meijer/Kroger/Target with status indicators
- Settings: profile, connected stores, notification toggles, theme switcher, sign out

Also adds:
- Mock data layer (src/lib/mock-data.ts) for demo/screenshot use
- StoreIcon component with store brand colors
- Code-split Recharts chunk (initial JS: 117KB, Recharts lazy: 498KB)
- All 48px+ touch targets, mobile-first Tailwind layout

Co-Authored-By: Paperclip <noreply@paperclip.ing>

package.json

@@ -0,0 +1,43 @@
+{
+  "name": "cartsnitch",
+  "private": true,
+  "version": "0.1.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "tsc -b && vite build",
+    "lint": "eslint .",
+    "preview": "vite preview",
+    "test": "NODE_ENV=test vitest run",
+    "test:watch": "NODE_ENV=test vitest"
+  },
+  "dependencies": {
+    "@tanstack/react-query": "^5.0.0",
+    "react": "^18.3.1",
+    "react-dom": "^18.3.1",
+    "react-router-dom": "^7.0.0",
+    "recharts": "^3.8.0",
+    "zustand": "^5.0.0"
+  },
+  "devDependencies": {
+    "@eslint/js": "^9.39.4",
+    "@tailwindcss/vite": "^4.0.0",
+    "@testing-library/jest-dom": "^6.6.3",
+    "@testing-library/react": "^16.3.2",
+    "@types/node": "^24.12.0",
+    "@types/react": "^18.3.28",
+    "@types/react-dom": "^18.3.7",
+    "@vitejs/plugin-react": "^4.5.2",
+    "eslint": "^9.39.4",
+    "eslint-plugin-react-hooks": "^7.0.1",
+    "eslint-plugin-react-refresh": "^0.5.2",
+    "globals": "^17.4.0",
+    "jsdom": "^25.0.1",
+    "tailwindcss": "^4.0.0",
+    "typescript": "^5.7.3",
+    "typescript-eslint": "^8.56.1",
+    "vite": "^6.3.5",
+    "vite-plugin-pwa": "^0.21.2",
+    "vitest": "^3.2.4"
+  }
+}