fix(core): pin next to ~16.1.6 to prevent 16.2 bumps (#2956)

Use tilde range to allow patch updates but block minor bumps to
16.2, which introduces deployment issues on Cloudflare Workers.

Author: matthewvolk

core/package.json

@@ -60,7 +60,7 @@
     "lodash.debounce": "^4.0.8",
     "lru-cache": "^11.1.0",
     "lucide-react": "^0.474.0",
-    "next": "^16.1.6",
+    "next": "~16.1.6",
     "next-auth": "5.0.0-beta.30",
     "next-intl": "^4.6.1",
     "nuqs": "^2.4.3",