[Task]: Fix Explorer link unfurling

[msarcev]

Task description

Since we moved to self-hosted, the previous solution for link unfurling doesn't work anymore.
Previously it was done with a vercel edge function that resolves the request for Explorer index.html an injects the metadata, you can find insight into this in client/api/index.js

This file should be removed an a new solution should be implemented more suitable for the current infrastructure (will need Thomas to help on this probably)