IMPORT-COUNTER-BUG: undatierte Wuerfe als WithoutDate zaehlen, nicht als Created

31 undatierte Wurfchronik-Eintraege (leeres Datumsfeld) wurden bei jedem Lauf
als littersCreated++ gezaehlt, weil ihr Idempotenz-Key (kein Datum) nie in
existingLitterKeySet stand -- aber kein DB-Insert folgte, da date is DateOnly d
false war. Das verfaelschte Arithmetik und Julians Bericht (752 vs 723).

Fix: undatierte Eintraege werden am Schleifenanfang uebersprungen
(littersWithoutDate++, continue) bevor sie in litterIdMap oder den
Created-Zaehler einfliessen. Execute-Block ohne redundante date-Pruefung.
Neues Feld LitterSummary.WithoutDate; Report-Notiz wenn WithoutDate > 0.

Gate: 126/126 C#-Tests, has-pending-model-changes = No.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

GerbilManager.Tests/ImportServiceTests.cs

@@ -507,6 +507,44 @@ namespace GerbilManager.Tests
             }
         }
 
+        [Fact]
+        public async Task UndatedLitters_counted_as_WithoutDate_not_Created()
+        {
+            // COUNTER-BUG regression: litters with no parseable date must go into WithoutDate,
+            // NOT Created. On re-import, Created must be 0 (not 31-phantom-phantom-phantom...).
+            var dir = Path.Combine(Path.GetTempPath(), "undated-" + Guid.NewGuid().ToString("N"));
+            Directory.CreateDirectory(dir);
+            try
+            {
+                // One dated litter, one undated litter (blank date field)
+                File.WriteAllText(Path.Combine(dir, "litters.json"), """
+                [
+                  {"id":"L-dated","litterId":"A","date":"01.02.2020","damName":"Mutter","sireName":"Vater","totalBorn":3,"zuchtnummer":"","note":""},
+                  {"id":"L-undated","litterId":"B","date":"","damName":"Mutter","sireName":"Vater","totalBorn":0,"zuchtnummer":"","note":""}
+                ]
+                """);
+                File.WriteAllText(Path.Combine(dir, "animals.json"), "[]");
+
+                using var db = NewDb();
+
+                // First run
+                var r1 = await new ImportService(db, dir, dir).RunAsync(execute: true);
+                Assert.Equal(2, r1.Litters.InSource);
+                Assert.Equal(1, r1.Litters.Created);        // only the dated one
+                Assert.Equal(0, r1.Litters.AlreadyImported);
+                Assert.Equal(1, r1.Litters.WithoutDate);    // the undated one
+                Assert.Equal(1, await db.Litters.CountAsync());  // only 1 persisted
+
+                // Second run (re-import): dated litter is now existing, undated still WithoutDate
+                var r2 = await new ImportService(db, dir, dir).RunAsync(execute: true);
+                Assert.Equal(0, r2.Litters.Created);        // no phantom "created"
+                Assert.Equal(1, r2.Litters.AlreadyImported);
+                Assert.Equal(1, r2.Litters.WithoutDate);
+                Assert.Equal(1, await db.Litters.CountAsync());  // still only 1 row
+            }
+            finally { try { Directory.Delete(dir, recursive: true); } catch { } }
+        }
+
         [Theory]
         [InlineData("01.02.2020", 2020, 2, 1)]
         [InlineData("5.3.21", 2021, 3, 5)]