OWNERSHIP: residency classification (Bestand vs external ancestors)

Per hive/agents/god/OWNERSHIP-residency.md (Julian): "Clan kleine Chaoten"
is the wife's own Zucht. Classify each animal:
 (a) RESIDENT if zuchtCanon contains 'kleinechaote' (separator/declension-
     insensitive: "v.d. Kleinen Chaoten", "Clan-Kleine-Chaoten", …); OR
 (b) PARENT EXCEPTION — a parent of a Clan offspring is resident even if its
     own Zuchtname is foreign (you can only breed a Clan litter if the parents
     were in your care). Runs AFTER the parentRefs→litter linking.
Otherwise EXTERNAL (pedigree ancestor, not living stock — kept, not deleted).

Stored as a dedicated Gerbil.IsResident bool (distinct from Status/Abgabe —
origin/identity, not current location), defaulting true (own stock unless
marked external; DB HasDefaultValue(true)). Additive migration
AddGerbilResidency; has-pending-model-changes clean. Round-trips in
GerbilDto/GerbilInput and is Gridify-filterable (isResident==true) so Kevin
can build a "nur Bestand" filter. ImportService computes it at (re-)import
and refreshes existing rows on the idempotent sweep. ResidencySummary added
to the import report.

Projected on real data: 306 loadable → 227 resident (188 rule a, +39 via
parent exception), 79 external ancestors.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

GerbilManagerWebAPI/Endpoints/GerbilEndpoints.cs

@@ -98,12 +98,13 @@ namespace GerbilManagerWebAPI.Endpoints
             g.CharacterTraits = i.CharacterTraits ?? new List<string>();
             g.CharacterNote = i.CharacterNote;
             g.IsDeaf = i.IsDeaf;
+            g.IsResident = i.IsResident ?? (isCreate ? true : g.IsResident);
         }
 
         internal static GerbilDto ToDto(Gerbil g) => new(
             g.Id, g.Name, g.Gender, g.Status, g.LitterId, g.OriginContactId, g.ReceiverContactId,
             g.EnclosureId, g.ColorVarietyId, g.DateOfBirth, g.DateOfDeath, g.CauseOfDeath,
             g.GoHomeDate, g.Genotype, g.Notes, g.ImportSource, g.ExternalRef, g.OriginBreeder,
-            g.CharacterTraits, g.CharacterNote, g.IsDeaf);
+            g.CharacterTraits, g.CharacterNote, g.IsDeaf, g.IsResident);
     }
 }