Custom sub domains: Allow wildcard subdomain routing within Base44

Allow wildcard subdomain routing within Base44. so that:

• the app routes to the same published app.

• The app can read the subdomain prefix (e.g. marcus) from the request/environment.

• SSL is handled automatically via wildcard certificate.

This would unlock a whole class of multi-tenant SaaS apps built on Base44 where each end-user or customer gets their own branded URL.