Consolidate shared configurations and simplify code structure

[tjementum]

Summary & Motivation

Consolidate shared configurations and simplify the code structure for better maintainability and consistency across self-contained systems.

Move ErrorPage and NotFoundPage to shared-webapp, and remove favicon.ico and robots.txt from the BackOffice self-contained system. Rename LandingPage to Home, and simplify main.tsx by removing null checks. Consolidate various configurations into the root package.json, including browserslist, and Tailwind PostCSS. Remove unused dependencies like react-aria-components and react-dom-confetti from each self-contained system.

Checklist

• [x] I have added a Label to the pull-request
• [x] I have added tests, and done manual regression tests
• [x] I have updated the documentation, if necessary

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[raix]

@tjementum nice work 🎉 - I did not trust that we could move the postcss and browserslist out in to the root package.json file, but learned something new 😃