fix: serialize `queryKey`

[KATT]

Serialize query keys the same way .data is serialized

Should fix https://github.com/trpc/trpc/issues/6802

Summary by CodeRabbit

• New Features
  • Query keys are now serialized during dehydrate/hydrate, enabling reliable round-tripping of complex keys (e.g., Date) between server and client.
• Bug Fixes
  • More robust hydration: queries are correctly reconstructed or updated with serialized keys and initial promise-based results are reused conditionally without altering fetch status.
• Tests
  • Expanded hydration tests covering non-primitive keys and serialization scenarios.
• Chores
  • Added a dev dependency to support test serialization.