feat: add basic layout with header, footer and main

[hestro]

This PR sets up the foundational page structure for the app.

Changes include:

• Set up global base styles: CSS reset, root variables, fonts, favicon
• Added Header component
  • The button in the header is currently not doing anything, and is just a placeholder for later development
• Added Footer component
• Added empty <main> content area in App.tsx
• CSS for each component is organized using CSS Modules

Note: This is my first time working with React - so don't hesitate to give feedback.

[martakam]

Everything looks good to go!