This makes the Vite assets handling better, namely:
- make it possible to include any vite assets in the templates
- include the right `<link rel="preload">` tags for assets
- include Subresource Integrity hashes
- pre-compress assets and remove on-the-fly compression by the Rust server
- build the CSS used by templates through Vite
It also moves the React app from /app/ to /account/, and remove some of the old SSR account screens.
It previously relied on the client being in the authorization grant,
which is not the case anymore. This commit also adds a test to ensure
we're not breaking this template in the future.
