Update exchange sync to use nimiq-website YAML

[Albermonte]

Summary

• replace the deprecated exchange API fetch with a sync from nimiq/nimiq-website's nuxt-content YAML collection
• copy upstream exchange logos into src/data/assets/exchanges so generated raw asset URLs stay publicly accessible
• regenerate exchange source and dist JSON data, including the new gateio.svg asset and refreshed coinpay.png
• add the yaml dependency required to parse upstream exchange definitions

Testing

• cd src && pnpm run build
• cd src && pnpm run typecheck
• cd src && pnpm run lint

[Albermonte]

Note: need to have nimiq-website repo open to public