fix: generate react-router types on install

Type-aware lint reads apps/web/.react-router/types, which only existed
after running typecheck or dev. CI runs pnpm verify (lint first) on a
fresh checkout, so vp lint failed with 15 missing-module errors. Run
react-router typegen as apps/web postinstall so the generated types
exist right after pnpm install.

Author: fengmk2

apps/web/package.json

@@ -8,6 +8,7 @@
     "build": "react-router build",
     "start": "react-router-serve build/server/index.js",
     "deploy": "wrangler deploy",
+    "postinstall": "react-router typegen",
     "test": "vp test run",
     "typecheck": "react-router typegen && tsc --noEmit"
   },