FEAT-8c: import loader — /import/dry-run + /import/execute (gated)

- Additive migration: Gerbil.RawImportData + Litter.PairingCode (Zuchtnummer der Verpaarung).
- ImportService consumes tools/import/output (animals.json + litters.json): litters first
  (authoritative), then conflict-free animals with a DOB; high-confidence (hoch) litter links
  set LitterId, date-only/ambiguous links quarantined; conflicts + stubs never loaded.
  Genotype mapped8locus -> frozen compact string; rawGenotype+unmappedTokens preserved in
  RawImportData; Farbschlag matched to ColorVariety; gender inferred from litter role;
  provenance ImportSource/ExternalRef; idempotent (ExternalRef / Name+Date). Photos copied to store.
- ImportEndpoints: POST /import/dry-run (no writes, Julian-readable report) + /import/execute (gated).

GerbilManagerWebAPI/Endpoints/ImportEndpoints.cs

@@ -0,0 +1,35 @@
+using GerbilManagerWebAPI.Import;
+using Microsoft.AspNetCore.Http.HttpResults;
+
+namespace GerbilManagerWebAPI.Endpoints
+{
+    /// <summary>
+    /// FEAT-8 stage 3 — spreadsheet import loader. Consumes tools/import/output.
+    ///   POST /import/dry-run  -> report what WOULD be created/linked/quarantined (no writes)
+    ///   POST /import/execute  -> load the conflict-free subset (idempotent). GATED: only run
+    ///                            against Julian's DB under god-supervision after he approves the dry-run.
+    /// </summary>
+    public static class ImportEndpoints
+    {
+        public static IEndpointRouteBuilder MapImportEndpoints(this IEndpointRouteBuilder app)
+        {
+            var group = app.MapGroup("/import").WithTags("Import");
+
+            group.MapPost("/dry-run", async Task<Ok<ImportReport>> (
+                ApplicationContext db, IConfiguration config, IWebHostEnvironment env) =>
+            {
+                var report = await new ImportService(db, config, env).RunAsync(execute: false);
+                return TypedResults.Ok(report);
+            });
+
+            group.MapPost("/execute", async Task<Ok<ImportReport>> (
+                ApplicationContext db, IConfiguration config, IWebHostEnvironment env) =>
+            {
+                var report = await new ImportService(db, config, env).RunAsync(execute: true);
+                return TypedResults.Ok(report);
+            });
+
+            return app;
+        }
+    }
+}