Perform dead code analysis with Knip (#2575)

* Install Knip

* Clarify an import that was confusing Knip

* Fix issues detected by Knip

Including cleaning up some unused code and dependencies, using a React hook that we unintentionally stopped using, and also adding some previously undeclared dependencies.

* Run dead code analysis in lint script and CI

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Co-authored-by: Timo <toger5@hotmail.de>

vitest.config.js

@@ -1,5 +1,5 @@
 import { defineConfig, mergeConfig } from "vitest/config";
-import viteConfig from "./vite.config";
+import viteConfig from "./vite.config.js";
 
 export default defineConfig((configEnv) =>
   mergeConfig(