refactor: migrate from vanilla JS to Next.js 16 with Tailwind CSS

- Replace vanilla HTML/CSS/JS with Next.js App Router + React components
- Game logic (champion-data, game-engine, classic-mode) moved to lib/
- UI split into modular components (game-board, champion-search, guess-grid, etc.)
- Add Tailwind CSS v4 with CSS variables for theming
- Immutable state updates, fetch deduplication, next/image for CDN images
- champions.json moved from assets/ to public/

web/package.json

@@ -0,0 +1,22 @@
+{
+  "name": "loldle",
+  "version": "0.1.0",
+  "private": true,
+  "scripts": {
+    "dev": "next dev",
+    "build": "next build",
+    "start": "next start",
+    "lint": "eslint"
+  },
+  "dependencies": {
+    "next": "16.2.2",
+    "react": "19.2.4",
+    "react-dom": "19.2.4"
+  },
+  "devDependencies": {
+    "@tailwindcss/postcss": "^4",
+    "eslint": "^9",
+    "eslint-config-next": "16.2.2",
+    "tailwindcss": "^4"
+  }
+}