Users, with their own settings, and a list of where each is signed in

The login is a user name and a password. The old single password becomes the account
named after the OS user on first boot, along with its sessions and the machine-wide look.
Settings gains Users (add, remove, reset a password — your own password confirms) and
Sessions (device, IP, last seen; revoke one or sign out everywhere else). Theme, accents
and the dashboard layout follow the account; the refresh rate, graph history and alerts
stay the machine's. Pairing a machine takes a user on it. Log lines name the actor.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

web/src/Shell.tsx

@@ -249,6 +249,7 @@ export default function Shell({ me: hubMe, onLoggedOut }: { me: Me; onLoggedOut:
         <span className="stat" title="load average, 1 · 5 · 15 min">load {me.load}</span>
         <span className={'dot ' + (online && !remoteErr ? 'ok' : 'bad')} title={remoteErr ? `${title} unreachable` : online ? 'connected' : 'disconnected'} />
         <Power host={me.host} label={title} rebootNeeded={me.reboot_needed} />
+        {hubMe.account && <span className="host account" title="signed in as">{hubMe.account}</span>}
         <Btn className="link" onClick={logout}>logout</Btn>
       </header>