chore: migrate from npm to pnpm

package.json

@@ -2,6 +2,7 @@
   "name": "rplace",
   "private": true,
   "type": "module",
+  "packageManager": "pnpm@11.1.1",
   "scripts": {
     "dev": "wrangler dev",
     "dev:client": "vite dev",
@@ -21,5 +22,8 @@
     "vite": "^6.3.2",
     "vitest": "^4.1.4",
     "wrangler": "^4.14.1"
+  },
+  "pnpm": {
+    "onlyBuiltDependencies": ["esbuild", "sharp", "workerd"]
   }
 }