chore(devkit): bump Next.js to 16.2.1 (#305)

## Summary
- bump `apps/devkit` Next.js dependency from `^16.2.0` to `^16.2.1`
- sync `pnpm-lock.yaml` to Next.js `16.2.1` and matching `@next/*`
artifacts
- keep scope limited to dependency update (no API/route/contract
changes)

## Testing
- `cd "apps/devkit" && pnpm test`
- `pnpm --filter devkit... build`
- `pnpm --filter devkit... exec next --version` (`Next.js v16.2.1`)

Author: kdy1

apps/devkit/package.json

@@ -16,7 +16,7 @@
     "@connectrpc/connect-query": "^2.2.0",
     "@connectrpc/connect-web": "^2.1.1",
     "@tanstack/react-query": "^5.90.21",
-    "next": "^16.2.0",
+    "next": "^16.2.1",
     "react": "^19.2.4",
     "react-dom": "^19.2.4"
   },