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/Models/Gerbil.cs

@@ -73,6 +73,13 @@ namespace GerbilManagerWebAPI.Models
         /// (dea/taub), false = hearing (Dea/hörend). Set by the FEAT-8 import from the
         /// after-spsp deafness annotation; see hive/agents/god/GENETIK-notation.md.</summary>
         public bool? IsDeaf { get; set; }
+
+        /// <summary>Residency/ownership (ORIGIN, distinct from Abgabe location): true = part of
+        /// the Clan-kleine-Chaoten Bestand, false = external pedigree ancestor (bred elsewhere).
+        /// Rule (a) Zuchtname matches the Clan kennel, OR (b) it's a parent of a Clan offspring.
+        /// Defaults true (manually-added animals are own stock); the FEAT-8 import classifies
+        /// imported animals. See hive/agents/god/OWNERSHIP-residency.md. Gridify-filterable.</summary>
+        public bool IsResident { get; set; } = true;
     }
 
     /// <summary>Shared normalisation for the separator-insensitive name search.</summary>