test(unit-tests): silence captured stdout in Testing env

The unit-test suite was spending most of its wall clock writing logs.
NUnit captures stdout per test and embeds it in the trx; with HttpLogging
emitting full request/response per controller call, EF Core SQL at
Information level, and ReferenceDataImporter banners running ~500x
(once per factory construction), the trx grew to 3.2 GB and the NUnit
result-XML serializer OOMed in StringBuilder.ToString() — which the
runner reported as one mysteriously failed test, masking a real
date-dependent failure underneath.

Three sources silenced under environment "Testing":
- appsettings.Testing.json drops Default + Microsoft.AspNetCore +
  HttpLoggingMiddleware + EntityFrameworkCore to Warning.
- Program.cs skips app.UseHttpLogging() entirely (avoids the
  middleware overhead, not just the log emission).
- ReferenceDataImporter takes optional TextWriters; the test factory
  passes TextWriter.Null. Per-importer helpers become instance methods
  so they can use the injected writer.

Result on a fresh run with ParallelScope.Fixtures already in place:
- Test duration: 1m46s -> 59s
- Wall clock: 2m23s -> 1m00s
- trx size: 3.2 GB -> 1.7 MB

The previously-masked date-dependent failure (PackControllerFullCatalog
.Info_returns_full_35_pack_catalog_from_production_seed asserting 35
active packs as of 2026-05-23 against a live clock) is now visible and
can be addressed separately.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SVSim.UnitTests/Infrastructure/SVSimTestFactory.cs

@@ -78,7 +78,8 @@ internal sealed class SVSimTestFactory : WebApplicationFactory<Program>
         // production uses so tests exercise the same code path. CardCosmeticRewards skipped —
         // FK to Cards would reject every row against the minimal 3-card test seed below.
         var dataDir = Path.Combine(AppContext.BaseDirectory, "Data");
-        new ReferenceDataImporter().ImportAllAsync(db, dataDir).GetAwaiter().GetResult();
+        new ReferenceDataImporter(TextWriter.Null, TextWriter.Null)
+            .ImportAllAsync(db, dataDir).GetAwaiter().GetResult();
 
         // Seed a minimal card set so card-pool tests can resolve a non-empty pool without
         // requiring the full CardImporter tool or a cards.json file. The set is marked