feat(health): hovering a user tile shows their login, role and today's spend

System Health's Users · CPU / RAM card: each tile's hover card names the login
name; for an admin or analyst it adds role, $ spent today, workspaces,
sessions and last sign-in from GET /api/users (staff-only, re-read every 60 s).
A developer's card shows the login name alone and never calls /api/users.

docs/SERVER-MODE.md

@@ -188,7 +188,9 @@ Workspaces made before server mode, or by the host account, have none.
   load, memory and swap, every real disk (HDD or SSD, how full; the one
   holding the users' homes is marked), any NVIDIA GPU. Each user's live
   share of it is a **Users · CPU / RAM now** card on the same tab (a tile per
-  user, their busiest processes on click; their home share stays in
+  user, their busiest processes on click; on hover their login name, and for an
+  admin or analyst — from `GET /api/users` — their role, $ spent today,
+  workspaces, sessions and last sign-in; their home share stays in
   Administration's users table), and the processes of no user are listed apart — CPU % of the whole machine (100 % = every core busy) and
   resident memory over a 1 s `/proc` sample, a process count, the busiest
   processes by their kernel name (never argv or env), and their home's size