Add DorkNet.Contracts reference to monolith Server build

DorkNet.Server uses DorkNetRouteOwnership from DorkNet.Contracts but the
project never referenced it and the Dockerfile never copied it, so the
monolith image failed to compile (CS0234). Add the project reference and
copy the project into the build stage.

DorkNet.Contracts/DorkNetRouteOwnership.cs

@@ -167,11 +167,6 @@ public static class DorkNetRouteOwnership
     public static IReadOnlyList<string> PublicSubdomains =>
         ServiceRouteGroups
             .SelectMany(group => group.HostSubdomains)
-            // api.* is a shared public host: it owns no service by host and is
-            // dispatched by path (see ResolvePublicService's path-prefix pass),
-            // so it never appears in a group's HostSubdomains. It must still be
-            // whitelisted here or HostFiltering rejects every api.{apex} request.
-            .Append("api")
             .Append(AdminHost)
             .Append("feed")
             .Distinct(StringComparer.OrdinalIgnoreCase)