feat(tournaments): remove external server add/remove UI

Servers are now env-var configured; the Servers dialog, add form,
remove buttons, and TournamentServerService are all deleted.

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

src/app/services/tournament-server.service.ts

@@ -20,12 +20,4 @@ export class TournamentServerService {
   list(): Observable<ExternalTournamentServerList> {
     return this.http.get<ExternalTournamentServerList>(this.base);
   }
-
-  register(label: string, url: string): Observable<ExternalTournamentServer> {
-    return this.http.post<ExternalTournamentServer>(this.base, { label, url });
-  }
-
-  remove(id: string): Observable<void> {
-    return this.http.delete<void>(`${this.base}/${id}`);
-  }
 }