url-prefix is not picked up in the footer links

[deepchatterjeeligo]

Describe the bug

The links in the footer lead to 404 when launching flower with --url-prefix.

To Reproduce
Steps to reproduce the behavior:

1. Launch flower with the --url-prefix. Here proj is any representative celery project.

celery -A proj flower --url-prefix=flower

Putting a trailing slash (as mentioned in #1207) does not help. Using --url-prefix=flower/ has the same behavior.

This starts flower at http://0.0.0.0:5555/flower/
2. Launch a few tasks from the celery project, so that there are non-zero processed tasks
3. Click on (or hover over) the number of processed tasks (in the above case, the value 10)
4. This redirects to http://0.0.0.0:5555/tasks and gives a 404 (screenshot below).

Expected behavior
It should have redirected to http://0.0.0.0:5555/flower/tasks. The url-prefix is missing.

Screenshots

System information
Output of python -c 'from flower.utils import bugreport; print(bugreport())' command

flower   -> flower:2.0.0 tornado:6.3.2 humanize:4.7.0
software -> celery:5.2.7 (dawn-chorus) kombu:5.2.4 py:3.10.8
            billiard:3.6.4.0 py-amqp:5.1.1
platform -> system:Linux arch:64bit, ELF
            kernel version:5.15.0-78-generic imp:CPython
loader   -> celery.loaders.app.AppLoader
settings -> transport:amqp results:disabled

deprecated_settings: None

[mher]

Fixed by #1297