test(udt-011): T400.40 — update tests for TimeProvider injection and explicit now params

Fix all test compilation errors caused by T400.10/T400.20/T400.30:
- Handler constructors: add TimeProvider.System as last argument
- Domain mutator calls: add DateTime.UtcNow as explicit 'now' argument
- AuditLogger/SecurityEventLogger Build() helpers: add TimeProvider.System
- JwtService test constructors: add TimeProvider.System
Cat2 coverage already present in TimeProviderArgentinaExtensionsTests.cs:
FakeTimeProvider proves GetArgentinaToday() returns ART civil date, not UTC.

tests/SIGCM2.Application.Tests/Medios/Reactivate/ReactivateMedioCommandHandlerTests.cs

@@ -19,7 +19,7 @@ public class ReactivateMedioCommandHandlerTests
 
     public ReactivateMedioCommandHandlerTests()
     {
-        _handler = new ReactivateMedioCommandHandler(_repo, _audit);
+        _handler = new ReactivateMedioCommandHandler(_repo, _audit, TimeProvider.System);
     }
 
     // ── not found → throws ──────────────────────────────────────────────────