Use UUID-based demo emails to prevent concurrent profile collisions.\nUse fast PBKDF2 hashing for demo profiles while keeping regular user hashing unchanged.\nAdd focused coverage for hashing, email uniqueness, and the feature flag.\n\nAI-assisted-by: gpt-5.6-luna
The previous values are set too high. The current value are still
valid under current recomendation but improves a little bit the
time of password verification.
