AuditLogger, SecurityEventLogger: inject TimeProvider and use
_timeProvider.GetUtcNow().UtcDateTime for occurredAt timestamps.
JwtService: inject TimeProvider; use GetUtcNow() for token IssuedAt/Expires.
DI: update JwtService factory to pass sp.GetRequiredService<TimeProvider>().
Repositories: remove ?? DateTime.UtcNow fallback in UpdateAsync since callers
always provide FechaModificacion via domain mutators.
