[chore:] implemented union (combiner) and its usage

Tasks/CombineAddresses.cs

@@ -21,6 +21,7 @@ public class CombineAddresses
         var res = await Task.Run(async () =>
         {
             if (type == "difference") return Difference(address_lists);
+            if (type == "union") return Union(address_lists);
 
             return null;
         });
@@ -89,12 +90,12 @@ public class CombineAddresses
     }
 
     public async Task<KasAddressList> Difference(List<KasAddressList> address_lists,
-        DifferenceProgress? progress = null)
+        Progress? progress = null)
     {
         if (address_lists == null || address_lists.Count == 0)
             return new KasAddressList("difference");
 
-        progress ??= new DifferenceProgress
+        progress ??= new Progress
         {
             TotalPersons = address_lists.Sum(l => l.KasPersons.Count),
             ComparedPersons = 0
@@ -126,11 +127,41 @@ public class CombineAddresses
     }
 
 
-    public async Task<KasAddressList> Union()
+    public async Task<KasAddressList> Union(List<KasAddressList> address_lists, Progress progress = null)
     {
-        return null;
+        var result = new KasAddressList("union");
+
+        if (address_lists == null || address_lists.Count == 0)
+            return result;
+
+        var total = address_lists.Sum(l => l.KasPersons.Count);
+        var processed = 0;
+
+        foreach (var list in address_lists)
+        foreach (var person in list.KasPersons)
+        {
+            if (!result.KasPersons.Any(existing => CompareAddresses(existing, person)))
+                result.KasPersons.Add(person);
+
+            processed++;
+            var percent = processed / (double)total * 100;
+            var logMessage =
+                $"{percent:F1}%: Person mit {person.refsid} hinzugefügt (aktuell {result.KasPersons.Count} Einträge)";
+
+            // Sicher, nicht blockierend:
+            if (progress != null)
+            {
+                if (Dispatcher.UIThread.CheckAccess())
+                    progress.LogAction?.Invoke(logMessage);
+                else
+                    Dispatcher.UIThread.Post(() => progress.LogAction?.Invoke(logMessage));
+            }
+        }
+
+        return result;
     }
 
+
     public async Task<KasAddressList> MoveDuplicatesToNew()
     {
         return null;
@@ -207,7 +238,7 @@ public class CombineAddresses
     // }
 }
 
-public class DifferenceProgress
+public class Progress
 {
     public int TotalPersons { get; set; } // Gesamtzahl der zu prüfenden Personen
     public int ComparedPersons { get; set; } // Schon verglichene Personen