REVIEW-FIXES-BACKEND: CR-9 + CR-11 + CR-10 + DB-1

CR-9 (major): gidByNameDob TryGetValue + ExternalRef-Fallback
  Verhindert KeyNotFoundException wenn Name/DOB zwischen zwei Laeufen driftet
  (z.B. correctDob-Remap oder UI-Umbenennung). Fallback: ExternalRef-Dict-Lookup;
  bei Miss: sauberes Ueberspringen + Note statt 500. +Test CR9_NameDOB_drift.

CR-11 (major): Farbschlag aus Genotyp ableiten (fill-NULL-only)
  Deep-Band-Tiere (gen>=2, kein Farbschlag-Feld) landen nicht laenger mit null
  ColorVariety. GenotypePotentiallyMatches() vergleicht locus-pair-weise (??=wildcard,
  case-insensitive). Nur vollstaendige Genotypen (8 Loci, kein ??) loesen Ableitung aus.
  Plan-Loop: fuellt colorVarietyId bei null + vollstaendigem Genotyp.
  Post-Sweep: bestehende DB-Tiere mit null ColorVarietyId werden nachgefuellt.
  AnimalSummary.FarbschlagDerivedFromGenotype = Zaehler. +Test CR11_ColorVariety_from_geno.

CR-10 (major, Python): malformed Override-Genotyp wird nicht angewendet
  apply_conflict_decisions validiert mapped8locus nach gt.parse(). Leeres Ergebnis
  = Genotyp unveraendert + decisionWarning statt stillem Blanken. Konflikt wird
  trotzdem aufgeloest (Entscheidung gilt, nur Genotyp-Override ausgelassen).
  +5 Python-Tests (CR-10-Block in test_extract.py).

DB-1 (high): filtered unique index auf Gerbil.ExternalRef
  WHERE ExternalRef IS NOT NULL — verhindert doppelten Import bei Race-Conditions
  oder Lauf-Ueberschneidungen. Migration UniqueExternalRef. SQLite-Testhost:
  HasFilter() wird via EnsureCreated appliziert (SQLite unterstuetzt Partial-Indexes).
  PartialUpdateTests externalRef-Assertion auf NotNull geaendert (name-hash unique).

GATE: 139/139 C# + Python ALL PASS, ef has-pending=No.

GerbilManager.Tests/ImportServiceTests.cs

@@ -580,6 +580,74 @@ namespace GerbilManager.Tests
             Assert.Equal(new DateOnly(y, m, d), date);
         }
 
+        [Fact]
+        public async Task CR9_NameDOB_drift_falls_back_to_ExternalRef_no_throw()
+        {
+            // CR-9: if an already-imported animal's Name or DOB in animals.json no longer matches
+            // what's stored in the DB (e.g. after a correctDob remap or manual UI rename), the
+            // gidByNameDob lookup used to throw KeyNotFoundException. Now it falls back to the
+            // stable ExternalRef without throwing.
+            var dir = Path.Combine(Path.GetTempPath(), "cr9-" + Guid.NewGuid().ToString("N"));
+            Directory.CreateDirectory(dir);
+            try
+            {
+                File.WriteAllText(Path.Combine(dir, "litters.json"), "[]");
+                File.WriteAllText(Path.Combine(dir, "animals.json"), """
+                [{"id":"drift","name":"Drift Tier","dob":"01.01.2021","death":"","farbschlag":"",
+                  "genotype":{"mapped8locus":{},"rawGenotype":"","unmappedTokens":[]},
+                  "conflict":false}]
+                """);
+                using var db = NewDb();
+                // Run 1: load the animal normally
+                await new ImportService(db, dir, dir).RunAsync(execute: true);
+                Assert.Equal(1, await db.Gerbils.CountAsync());
+
+                // Simulate drift: manually rename the animal in the DB (UI rename scenario)
+                var g = await db.Gerbils.SingleAsync(x => x.ExternalRef == "drift");
+                g.Name = "Umbenannt Tier";
+                await db.SaveChangesAsync();
+
+                // Run 2: animals.json still has old name "Drift Tier" — must NOT throw
+                var report2 = await new ImportService(db, dir, dir).RunAsync(execute: false);
+                // Dry-run should complete without throwing; animal is found by ExternalRef fallback
+                Assert.Equal(1, await db.Gerbils.CountAsync());   // no duplicate created
+            }
+            finally { try { Directory.Delete(dir, recursive: true); } catch { } }
+        }
+
+        [Fact]
+        public async Task CR11_ColorVariety_derived_from_genotype_when_no_explicit_farbschlag()
+        {
+            // CR-11: deep-band animals have empty Farbschlag but a full genotype. The loader
+            // must derive ColorVarietyId from the catalog when the name-match yields nothing.
+            // "Agouti" = aa CC DD EE GG PP spsp rere (first seed entry, ID 00000001).
+            var dir = Path.Combine(Path.GetTempPath(), "cr11-" + Guid.NewGuid().ToString("N"));
+            Directory.CreateDirectory(dir);
+            try
+            {
+                File.WriteAllText(Path.Combine(dir, "litters.json"), "[]");
+                // Exact Agouti genotype, no explicit Farbschlag name
+                File.WriteAllText(Path.Combine(dir, "animals.json"), """
+                [{"id":"agouti-deep","name":"Opa Waldmann","dob":"01.01.2018","death":"","farbschlag":"",
+                  "genotype":{"mapped8locus":{"A":["a","a"],"C":["C","C"],"D":["D","D"],"E":["E","E"],"G":["G","G"],"P":["P","P"],"Sp":["sp","sp"],"Re":["re","re"]},
+                              "rawGenotype":"aa CC DD EE GG PP spsp rere","unmappedTokens":[]},
+                  "conflict":false}]
+                """);
+                using var db = NewDb();
+                var report = await new ImportService(db, dir, dir).RunAsync(execute: true);
+
+                var tier = await db.Gerbils.SingleAsync(g => g.ExternalRef == "agouti-deep");
+                // ColorVarietyId must be set even though no explicit Farbschlag name was given
+                Assert.NotNull(tier.ColorVarietyId);
+                // Should be the "Agouti" variety (id = 00000000-0000-0000-0000-000000000001)
+                var variety = await db.ColorVarieties.FindAsync(tier.ColorVarietyId);
+                Assert.Equal("Agouti", variety!.Name);
+                // Report counter should reflect the genotype derivation
+                Assert.True(report.Animals.FarbschlagDerivedFromGenotype > 0);
+            }
+            finally { try { Directory.Delete(dir, recursive: true); } catch { } }
+        }
+
         // ---- fixtures ----
         private const string LittersJson = """
         [