Add Scholia banner regarding the graph split

[Daniel-Mietchen]

Is your feature request related to a problem? Please describe.
The graph split is affecting Wikidata and Scholia, so Scholia users should be informed about it.

Describe the solution you'd like
We should set up a banner on all Scholia pages (ideally such that it can be clicked away) that points to the dedicated on-wiki page https://www.wikidata.org/wiki/Wikidata:Scholia/Wikidata_graph_split_2024 where we provide some background information and (eventually, as per #2548 ), a user survey.

Describe alternatives you've considered
We could have no such banner or only on the Scholia homepage, or with multiple links.

Additional context
A similar note is currently on display at the Wikidata Query Service homepage, [https://query.wikidata.org/ https://query.wikidata.org/]: