Per-connection user management for IBM i

Administrators now provision managed users, identity policy, device names, and session limits for each AS/400 connection instead of one global list. JWT, Kerberos, and trusted-header settings follow the selected connection, so one host can require external identity while another stays open. Import and export users with CSV, including multiple device names and output queues per person. Username matching is case-insensitive, so launch tokens still resolve when letter case differs from the stored user.