build: remove unused esbuild-css-modules-plugin

[jrieken]

Summary

Remove the completely unused esbuild-css-modules-plugin devDependency from our project, as our esbuild.mjs natively configures the .css loader as text.

Session Context

Key decisions from the development session:

• Redundant plugin: The esbuild-css-modules-plugin plugin isn't referenced anywhere in the esbuild.mjs script, and CSS files are resolved explicitly via loader: { '.css': 'text' }. Therefore, the plugin was removed entirely.
• Verification: The package.json was updated, npm install applied the changes to package-lock.json, and running npm run compile-lint-test alongside a manual test of npm run esbuild confirmed no breakages.

Changes

• Removed "esbuild-css-modules-plugin" from package.json devDependencies
• Regenerated package-lock.json