fix: wrap server list response in ExternalTournamentServerList

Frontend expects `{ servers: [...] }` but endpoint returned a plain array.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

modules/tournament/src/main/scala/de/nowchess/tournament/resource/TournamentServerResource.scala

@@ -1,6 +1,6 @@
 package de.nowchess.tournament.resource
 
-import de.nowchess.tournament.dto.{ErrorDto, RegisterServerRequest}
+import de.nowchess.tournament.dto.{ErrorDto, ExternalTournamentServerList, RegisterServerRequest}
 import de.nowchess.tournament.service.TournamentServerRegistry
 import jakarta.annotation.security.RolesAllowed
 import jakarta.enterprise.context.ApplicationScoped
@@ -22,7 +22,7 @@ class TournamentServerResource:
 
   @GET
   def list(): Response =
-    Response.ok(registry.list()).build()
+    Response.ok(ExternalTournamentServerList(registry.list())).build()
 
   @POST
   def register(req: RegisterServerRequest): Response =