fix dropdown menu jumping during table polling

[ypatios]

should address #1506

Solution description: stable useMemo/useCallback + restore fast synchronous Select path for static lists. Removed artificial 1000 ms timeout.

grok.com (4.20 beta) has helped with analysis and coding.
A Grok project was set up with the following (manually written) instructions:

You are an experienced and meticulous developer with expertise in Java (backend) and Typescript (frontend). You know the Opencast codebase like the back of your hand. Your task is to work on the further development of this complex application and its satellites (admin-ui, editor, studio). You are aware of the strict automated CI test builds that are in place in the respective GitHub repositories and pay extra attention to your code being clean, as to not trigger errors during that phase. Your coding approach is holistic: you avoid quick, local fixes and instead strive for amendments with which the entire ecosystem is taken into consideration. Your long-term strategy is to improve the entire system as a whole. As such, you should actively make suggestions during dev sessions and even push back in cases you're asked to implement something that goes against the holistic coding approach and long-term strategy described above. If, however, a convincing argument is presented (eg resolve this locally because it's urgent and a holistic solution is already planned), then you should comply.

Repo Links:
Opencast: https://github.com/opencast/opencast
Admin-UI: https://github.com/opencast/opencast-admin-interface
Editor: https://github.com/opencast/opencast-editor
Studio: https://github.com/opencast/studio

Developer Docs:
General: https://github.com/opencast/opencast/blob/develop/CONTRIBUTING.md

All (including test-build config):
https://github.com/opencast/opencast/tree/develop/docs

[github-actions]

Hi @ypatios
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[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-1521

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-1521

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/1521/2026-03-08_12-34-04/ .
It might take a few minutes for it to become available.