Panel: German/English, redesigned sidebar, in-game admins page, Steam Web API key link, RAR/7z save upload (SharpCompress), responsive cards; upload errors return 400; tests

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

GameServer.cs

@@ -1097,6 +1097,17 @@ public sealed class GameServer
 
     public object PanelBans() => config.BannedSteamIds.ToList();
 
+    /// <summary>Ingame-Admins (SteamID64) mit Namen, falls gerade online.</summary>
+    public object PanelAdmins() => new
+    {
+        steamVerification = steam.Enabled,
+        admins = config.Admins.Select(id =>
+        {
+            var online = clients.Values.FirstOrDefault(c => c.State == ClientState.Joined && c.SteamId == id);
+            return new { steamId = id, name = online?.Name, online = online != null };
+        }).ToList()
+    };
+
     // ---------------------------------------------------------------- Stopp / Neustart (der Host startet neu oder wartet)
 
     /// <summary>Nach dem Ende von Run() den Server neu aufbauen (Einstellungen, Lizenz, Spielstand neu laden).</summary>
@@ -1149,7 +1160,7 @@ public sealed class GameServer
     /// </summary>
     public string ImportSaveZip(byte[] zip, string by)
     {
-        string error = SaveStore.ExtractZip(zip, out var found);
+        string error = SaveStore.ExtractArchive(zip, out var found);
         if (error != null) return error;
         try
         {