feat: org admin access to team management — backend auth, UI visibility, tests
- Add _is_user_org_admin_for_team() reusable helper to common_utils.py
- Grant org admins access to /team/list, /team/info, /team/member_add,
/team/member_delete, /team/member_update, /team/model/add,
/team/model/delete, /team/permissions_list, /team/permissions_update
- Make validate_membership async with org admin fallback
- Add /user/list to self_managed_routes (endpoint handles own auth)
- UI: org admins see Members, Member Permissions, Settings tabs in team view
- UI: CreateUserButton uses useOrganizations() for org dropdown
- UI: org admin delete-member respects disable_team_admin_delete_team_user
- Add 16 unit tests for _is_user_org_admin_for_team, validate_membership,
_user_is_org_admin route check, and privilege escalation prevention
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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