Fix CI: Add demo package-lock.json and clean up code

- Add demo package-lock.json to fix CI npm ci failures
- Update .gitignore to allow demo lockfiles for CI reproducibility
- Clean up all ESLint warnings in main source and tests
- Remove Tailwind CSS dependencies, keep Carbon Components
- Fix accessibility issues with aria-label attributes
- Fix Vite build issues with node polyfills
- Clean up playwright test artifacts

Author: NiKrause

.gitignore

@@ -120,7 +120,8 @@ examples/**/.env.*
 
 # Examples node_modules (in case someone runs npm install in examples)
 examples/**/node_modules/
-examples/**/package-lock.json
+# Keep demo lockfiles for CI reproducibility
+# examples/**/package-lock.json
 examples/**/yarn.lock
 examples/**/pnpm-lock.yaml