Add role-based admin panel with root/admin/mod/user hierarchy
- User model: new 'role' column (root > admin > mod > user)
- End3r (id=2) set as 'root' (GOD admin)
- Admin panel modal: Users tab (search, set roles, verify, grant AI),
Bans tab (list/unban), Mutes tab (list/unmute)
- Role-based permission checks: root can set admins, admins set mods,
mods can kick/ban/mute/verify
- Shield icon in header (visible to mod+) opens admin panel
- Nicklist shows role icons: crown (root), swords (admin), shield (mod)
- Context menu: added Mute/Unmute action
- Live role_updated event pushes role changes to online users
- role_power hierarchy prevents privilege escalation
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