Broken documentation links in UI for unreleased/dev versions

### Apache Airflow version

main (dev) / latest

### What happened and how to reproduce it?

The Airflow UI constructs documentation links using the exact Airflow version (e.g., 3.2.0). For unreleased or development versions, the corresponding documentation may not yet be published, resulting in broken links (404 errors) when users try to access documentation from the UI.

Additionally, in NothingFoundInfo.tsx, the link uses an incorrect HTML attribute (target="blank" instead of _blank).

### What you think should happen instead?

1. Documentation links should always resolve to a valid page
2. For unreleased or development versions, the UI should fall back to stable documentation
3. Links should use correct HTML attributes (target="_blank" with rel="noopener noreferrer")

### Operating System

Any

### Versions of Apache Airflow Providers

_No response_

### Deployment

None

### Deployment details

_No response_

### Anything else?

- This issue occurs consistently when running unreleased/dev versions

- It directly impacts user experience by providing broken help/documentation links

### Are you willing to submit PR?

- [x] Yes I am willing to submit a PR!

### Code of Conduct

- [x] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)