setup typechecking and fix build errors

package.json

@@ -4,7 +4,8 @@
   "scripts": {
     "dev": "vite --host 0.0.0.0",
     "build": "vite build",
-    "preview": "vite preview"
+    "preview": "vite preview",
+    "typecheck": "tsc --noEmit"
   },
   "dependencies": {
     "@tensorflow/tfjs": "^4.19.0",
@@ -13,9 +14,11 @@
     "react-router-dom": "^7.15.0"
   },
   "devDependencies": {
+    "@types/node": "^25.6.2",
     "@types/react": "^18.3.5",
     "@types/react-dom": "^18.3.0",
     "@vitejs/plugin-react": "^4.3.0",
+    "typescript": "^6.0.3",
     "vite": "^5.4.0"
   }
 }