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.
