Add Nuxt4 support

### Make histoire Nuxt 4 ready

As a developer using Histoire I want the Histoire plugin to fully support Nuxt 4,
so that I can preview, document, and test my UI components directly within my Nuxt 4 project without manual configuration or compatibility issues.

### Suggested solution

TODO

### Alternative

_No response_

### Additional context

_No response_

### Validations

- [x] Follow our [Code of Conduct](https://github.com/histoire-dev/histoire/blob/main/CODE_OF_CONDUCT.md)
- [x] Read the [Contributing Guidelines](https://github.com/histoire-dev/histoire/blob/main/CONTRIBUTING.md).
- [x] Read the [docs](https://histoire.dev/guide/).
- [x] Check that there isn't [already an issue](https://github.com/histoire-dev/histoire/issues) that requests the same feature to avoid creating a duplicate.

No files or tests are identified in the issue. Start by locating Histoire's Nuxt integration and checking its behavior in a Nuxt 4 project; done means Nuxt 4 users can preview, document, and test components without manual configuration or compatibility issues.

Written by the indexing model from the issue text.