Query: consider a proxy for `client`/`cache` getters to control access

## Context

`Query#client` and `Query#cache` currently return the internal `QueryClient`/`QueryCache` instances directly:

https://github.com/equinor/fusion-framework/blob/main/packages/utils/query/src/Query.ts

```ts
public get client(): QueryClient {
return this.#client;
}

public get cache(): QueryCache {
return this.#cache;
}
```

There are long-standing `TODO: Proxy` comments suggesting these getters should return a proxy instead, to restrict/observe what consumers can do with the underlying instances (e.g. prevent calling internal-only methods directly).

## Task

- Decide whether a proxy is actually warranted, and if so, design its restricted surface.
- Implement the proxy (or remove the TODO if no longer considered necessary).

This issue was opened while resolving `fusion-lint`'s `no-todo-without-issue` rule, which requires TODO comments to reference a tracking issue.

Start with packages/utils/query/src/Query.ts and inspect the existing Query#client and Query#cache getters plus their TODO: Proxy comments. Decide whether restricting or observing the underlying QueryClient and QueryCache is warranted, define the allowed surface if it is, and finish by implementing the proxy or removing the TODO when no proxy is needed.

Written by the indexing model from the issue text.