Resolve conflicts in app/auth.py and app/api/admin_users.py:
- auth.py: combine admin-aware profile creation (from main, adding
is_complimentary/highest-tier defaults for admins) with signup
notification/webhook (from our branch). Admin users skip the
signup notification since they are the ones being notified.
- admin_users.py: combine is_complimentary assignment (from main)
with tier_changed/new_tier tracking variables (from our branch)
to fire plan-change notifications when an admin updates a user.