Making user's project the root for Vite POC

[infomiho]

Description

This PR is not for reviewing. It might serve for discussion later on.

What was done:

• Run npx vite from the user project dir and not .wasp/out/web-app
• Move index.html to user-land which loads the index.tsx
• Move index.tsx that mounts the React app to user-land
• Move public/manifest.json to user-land
• Moves the web-app code to the SDK
  • The router can't import user code directly since the SDK lives in the node_modules. Instead, it needs to import the user code from the src dir that was copied into the SDK.

Part of #3135 #3472