Co-op campaign "League against the Lightwatch": 20 missions, selectable on the Match page

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

lang/de.lang

@@ -660,6 +660,7 @@ net.coop_mission = Koop-Kampagne: Mission {0} ({1})
 net.coop_create = Koop-Kampagne
 net.coop_editor = Editor-Kampagne
 net.coop_builtin = Eingebaute Kampagne
+net.coop_league = Bund gegen die Lichtwacht
 net.coop_editor_mission = Editor-Kampagne {0}: Mission {1} ({2})
 net.coop_editor_none = Keine Mission der Editor-Kampagne passt für Koop (Karte mindestens 72x72, ein Ziel außer Rivalen-Meistern)
 net.join = Beitreten