GitHub App import for site admins

### Describe the issue

`/create/component/github-app/` seems to list all user accessible GitHub connected accounts. Once the user is site admin it seems to list all, what will not really scale for Hosted Weblate or other larger instances.

### I already tried

- [x] I've read and searched [the documentation](https://docs.weblate.org/).
- [x] I've searched for similar filed issues in this repository.

### Steps to reproduce the behavior

1. Visit `/create/component/github-app/` as site admin

### Expected behavior

- Workspace selection first to limit the amount
- Add pagination as even workspace can have a lot of repos

### Screenshots

_No response_

### Exception traceback

```pytb

```

### How do you run Weblate?

Git checkout

### Weblate version

main

### Weblate deploy checks

```shell

```

### Additional context

_No response_