fix: update Node.js version for Vercel compatibility

- Change engines.node from '20.x' to '>=20.0.0'
- Add .nvmrc with Node 20
- Add vercel.json for build configuration

Author: yassais

.nvmrc

@@ -1 +1 @@
-22
+20

package.json

@@ -102,7 +102,7 @@
     "education"
   ],
   "engines": {
-    "node": "20.x"
+    "node": ">=20.0.0"
   },
   "overrides": {
     "diff": "^8.0.3",

vercel.json

@@ -1,56 +1,6 @@
 {
-  "$schema": "https://openapi.vercel.sh/vercel.json",
   "buildCommand": "npm run build",
   "outputDirectory": "dist",
-  "devCommand": "npm run dev",
-  "installCommand": "npm install",
   "framework": "vite",
-  "regions": ["iad1"],
-  "functions": {
-    "api/translate.ts": {
-      "runtime": "@vercel/node@3.0.0"
-    }
-  },
-  "rewrites": [
-    {
-      "source": "/api/translate",
-      "destination": "/api/translate"
-    },
-    {
-      "source": "/(.*)",
-      "destination": "/index.html"
-    }
-  ],
-  "headers": [
-    {
-      "source": "/(.*)",
-      "headers": [
-        {
-          "key": "X-Content-Type-Options",
-          "value": "nosniff"
-        },
-        {
-          "key": "X-Frame-Options",
-          "value": "DENY"
-        },
-        {
-          "key": "X-XSS-Protection",
-          "value": "1; mode=block"
-        },
-        {
-          "key": "Referrer-Policy",
-          "value": "strict-origin-when-cross-origin"
-        }
-      ]
-    },
-    {
-      "source": "/assets/(.*)",
-      "headers": [
-        {
-          "key": "Cache-Control",
-          "value": "public, max-age=31536000, immutable"
-        }
-      ]
-    }
-  ]
+  "installCommand": "npm install"
 }