SEED-REW: rename ColorVariety 'Pink Eyed White (PEW)' to 'REW'

Single UpdateData migration for ID 00000000-...-0001 (sortOrder 0).
Name-only rename, genotype/ID/FK unchanged — no drift risk.
Matches colorVarietySeed.backend.json after GEN-4c (main 3aa9ac9).

165/165 tests, ef has-pending=No.

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

GerbilManagerWebAPI/Migrations/ApplicationContextModelSnapshot.cs

@@ -216,7 +216,7 @@ namespace GerbilManagerWebAPI.Migrations
                         {
                             Id = new Guid("00000000-0000-0000-0000-000000000001"),
                             CanonicalGenotype = "AA chch DD EE GG pp spsp rere",
-                            Name = "Pink Eyed White (PEW)",
+                            Name = "REW",
                             SortOrder = 0
                         },
                         new