fix(users): every user row shows its avatar, not only its initials

System Health's per-user CPU/RAM card asked UserAvatar for the viewer's own
picture with no user id, and the host stats never carried avatarAt, so every
card fell back to letters. The groups now carry avatarAt and the card passes
userId. The user editor's header, the pool board's member chips and the pool
member picker drew hand-made initials; they use UserAvatar too.

client/src/components/users/MemberPicker.tsx

@@ -13,6 +13,7 @@ import { useTranslation } from "react-i18next";
 import { Search } from "lucide-react";
 import type { AuthUser, ServerUserUsage } from "../../lib/api";
 import { Checkbox } from "../Checkbox";
+import { UserAvatar } from "./UserAvatar";
 
 export const ROLES: AuthUser["role"][] = ["admin", "developer", "analyst"];
 /** A role, every user, or the users in no pool group. */
@@ -168,7 +169,14 @@ export function MemberPicker({
               checked={chosen.has(u.id)}
               onChange={(on) => setMany([u.id], on)}
               label={
-                <span>
+                <span className="inline-flex items-center gap-1.5">
+                  <UserAvatar
+                    name={u.displayName || u.username}
+                    userId={u.id}
+                    avatarAt={u.avatarAt}
+                    letters={1}
+                    className="h-5 w-5 text-[10px]"
+                  />
                   {u.username}
                   {u.disabled && <span className="ml-1 text-fg-muted">({t("disabled")})</span>}
                   {note?.(u)}