docs: record LAB-02 idempotency evidence

[haydarkozat]

LAB-02 evidence

• records successful -WhatIf validation for eight fictitious test identities
• records that all eight identities are present in the lab tenant
• records second-run idempotency: 8 x Skipped with Benutzer existiert bereits.
• avoids claiming unobserved first-run terminal output
• no passwords, tenant IDs, object IDs, or personal account identifiers committed

Portal verification and department-group assignment remain open.