Bump ai from 4.1.34 to 5.0.52 in /samples/mastra-nextjs/app

Bumps [ai](https://github.com/vercel/ai) from 4.1.34 to 5.0.52.
- [Release notes](https://github.com/vercel/ai/releases)
- [Changelog](https://github.com/vercel/ai/blob/main/CHANGELOG.md)
- [Commits](https://github.com/vercel/ai/compare/ai@4.1.34...ai@5.0.52)

---
updated-dependencies:
- dependency-name: ai
  dependency-version: 5.0.52
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

samples/mastra-nextjs/app/package.json

@@ -23,7 +23,7 @@
     "@radix-ui/react-slot": "^1.1.2",
     "@radix-ui/react-tooltip": "^1.1.8",
     "@tailwindcss/postcss": "^4.0.6",
-    "ai": "^4.1.34",
+    "ai": "^5.0.52",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
     "dotenv": "^16.4.7",