improve region initialization and fix parallel geometry segfault

[nkrah]

Fix segfault when a region is attached to a volume in a parallel world.

The root cause was the region lifecycle introduced around the G4-DNA work: regions could be initialized too early, before parallel-world logical volumes existed. That timing pressure comes from the DNA EM physics activator, which needs region names/configuration available before physics construction, but the actual G4Region attachment must wait until the corresponding logical volumes have been constructed.

This PR changes the region initialization workflow accordingly:

• attach regions lazily as each root logical volume is constructed, in both the mass world and parallel worlds
• keep production cuts and user limits initialization after G4RunManager.Initialize()
• add early validation for inconsistent region configuration

This preserves the DNA-region workflow while avoiding the premature attachment that caused the segfault.