[Feature Request][Awesome] Add "back to overview" navigation for multi-plugin reports

### What problem should this solve?

When config defines multiple plugin-awesome reports, the root `index.html` links to all of them. However, once a sub-report is opened, there is no way to navigate back to the overview.

### What would you like to happen?

When multiple plugin-awesome reports are generated, each sub-report should provide a way to navigate back to the root overview. The goal is to be able to return to the overview from any sub-report without relying on the browser's back button.

### Alternatives considered

_No response_

### Additional context

_No response_

Start at the root index.html links and trace how multi-plugin sub-reports are generated and rendered. Add navigation from every sub-report back to the root overview, then verify that reports generated with multiple plugin-awesome reports can return to the overview without using the browser back button.

Written by the indexing model from the issue text.