Broadcasting logout event in order to redirect other tabs to login page

[ferishili]

This PR fixes #1194,

It introduces a broadcasting mechanism (to contain further implementation for other places as well), focusing on logout event.

On the App level we first subscribe to the broadcasting event, and on the Header => MenuUser on logout we broadcast the actual logout!

The actual tab is going to logout which redirects to j_spring_security_logout, but the other opened tabs will be redirected to login page with a 750 ms wait!

[github-actions]

Use docker or podman to test this pull request locally.

Run test server using develop.opencast.org as backend:

podman run --rm -it -p 127.0.0.1:3000:3000 ghcr.io/opencast/opencast-admin-interface:pr-1274

Specify a different backend like stable.opencast.org:

podman run --rm -it -p 127.0.0.1:3000:3000 -e PROXY_TARGET=https://stable.opencast.org ghcr.io/opencast/opencast-admin-interface:pr-1274

It may take a few seconds for the interface to spin up.
It will then be available at http://127.0.0.1:3000.
For more options you can pass on to the proxy, take a look at the README.md.

[github-actions]

This pull request is deployed at test.admin-interface.opencast.org/1274/2025-05-14_10-00-49/ .
It might take a few minutes for it to become available.

[rlucke]

looks fine to me and works as well