Dashboard does not redirect to status from prefix root.

[icykip]

Describe the issue:
Currently when specifying a prefix, the redirect behavior you get for the root is not replicated for the root of the prefix.

Minimal Complete Verifiable Example:

Run: dask scheduler --dashboard-address localhost:8080 --dashboard-prefix /prefix/
Go To: http://localhost:8050/prefix/status -> 200
Go To: http://localhost:8050/prefix/ -> 404
Go To: http://localhost:8050/ -> 302

Anything else we need to know?:
Put this under bug given my understanding that this would deviate from Bokeh app behavior but happy to move it to feature if thats a better fit.

Environment:

• Dask version: 2025.2.0
• Python version: 3.13.2
• Operating System: MacOS
• Install method (conda, pip, source): pip