Statements cannot be added locally through the GUI

[eloiferrer]

Issue description: In local development, statements cannot be added manually through the GUI. Properties and items created locally are not found because they are searched in the production site due to the hardcoded urls here: https://github.com/MaRDI4NFDI/portal-compose/commit/f3abbe1fc0cbcfeec5df0c0132f880b8362bbe62

TODOS: Probably update Wikibase.php with env variables.

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• [ ] Code was merged
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