feat(web): add-user form + delete confirmation in user management

- New AddUserFormClient on /settings/users (admin-only): username +
  password + role select. Wraps createUserAction.
- UserRowClient gains an isLastAdmin prop and a confirm-dialog before
  delete. Demote and Delete are both disabled on the last remaining
  admin so an admin can't lock everyone out via the UI (server-side
  guards in users.ts already cover the API).
- Page passes isLastAdmin per row and computes adminCount once.
- Role badge uses emerald for admin / slate for user; explicit Promote
  / Demote arrows replace the bidirectional icon.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/src/app/settings/users/add-user-form-client.tsx

@@ -0,0 +1,95 @@
+"use client";
+
+import { useState, useTransition } from "react";
+import { Loader2Icon, UserPlusIcon } from "lucide-react";
+import { Button } from "@/components/ui/button";
+import { Input } from "@/components/ui/input";
+import { Label } from "@/components/ui/label";
+import { createUserAction } from "@/actions/users";
+
+export function AddUserFormClient() {
+  const [pending, start] = useTransition();
+  const [username, setUsername] = useState("");
+  const [password, setPassword] = useState("");
+  const [role, setRole] = useState<"admin" | "user">("user");
+  const [error, setError] = useState<string | null>(null);
+  const [ok, setOk] = useState(false);
+
+  function submit() {
+    start(async () => {
+      setError(null);
+      setOk(false);
+      const r = await createUserAction({
+        username: username.trim(),
+        password,
+        role,
+      });
+      if (!r.ok) {
+        setError(r.error);
+        return;
+      }
+      setUsername("");
+      setPassword("");
+      setRole("user");
+      setOk(true);
+    });
+  }
+
+  return (
+    <div className="space-y-3">
+      <div className="grid grid-cols-1 gap-3 sm:grid-cols-2">
+        <div className="space-y-1.5">
+          <Label htmlFor="new-username">Username</Label>
+          <Input
+            id="new-username"
+            value={username}
+            onChange={(e) => setUsername(e.target.value)}
+            autoComplete="off"
+            maxLength={256}
+            placeholder="alice"
+          />
+        </div>
+        <div className="space-y-1.5">
+          <Label htmlFor="new-password">Password</Label>
+          <Input
+            id="new-password"
+            type="password"
+            value={password}
+            onChange={(e) => setPassword(e.target.value)}
+            autoComplete="new-password"
+            maxLength={256}
+            placeholder="≥10 characters"
+          />
+        </div>
+      </div>
+      <div className="space-y-1.5">
+        <Label htmlFor="new-role">Role</Label>
+        <select
+          id="new-role"
+          value={role}
+          onChange={(e) => setRole(e.target.value === "admin" ? "admin" : "user")}
+          className="h-9 w-full rounded-md border border-input bg-transparent px-2 text-sm focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring"
+        >
+          <option value="user">user</option>
+          <option value="admin">admin</option>
+        </select>
+      </div>
+      <div className="flex items-center justify-end gap-2">
+        {error && <p className="mr-auto text-xs text-destructive">{error}</p>}
+        {ok && (
+          <p className="mr-auto text-xs text-emerald-600 dark:text-emerald-400">
+            User created.
+          </p>
+        )}
+        <Button type="button" size="sm" disabled={pending} onClick={submit}>
+          {pending ? (
+            <Loader2Icon className="size-4 animate-spin" />
+          ) : (
+            <UserPlusIcon className="size-4" />
+          )}
+          Add user
+        </Button>
+      </div>
+    </div>
+  );
+}

apps/web/src/app/settings/users/page.tsx

@@ -1,28 +1,58 @@
 import { requireAdmin } from "@/lib/auth";
 import { db } from "@/lib/db";
 import { PageShell } from "@/components/page-shell";
-import { Card, CardContent } from "@/components/ui/card";
+import {
+  Card,
+  CardContent,
+  CardDescription,
+  CardHeader,
+  CardTitle,
+} from "@/components/ui/card";
 import { UserRowClient } from "./user-row-client";
+import { AddUserFormClient } from "./add-user-form-client";
 
 export default async function UsersPage() {
   const me = await requireAdmin();
   const rows = await db.query.operators.findMany({
     orderBy: (o, { asc }) => [asc(o.username)],
   });
+  const adminCount = rows.filter((r) => r.role === "admin").length;
 
   return (
     <PageShell title="Users">
       <Card>
-        <CardContent className="space-y-3 py-4">
+        <CardHeader>
+          <CardTitle>Add user</CardTitle>
+          <CardDescription>
+            Create a sign-in account. Passwords must be at least 10
+            characters.
+          </CardDescription>
+        </CardHeader>
+        <CardContent>
+          <AddUserFormClient />
+        </CardContent>
+      </Card>
+
+      <Card>
+        <CardHeader>
+          <CardTitle>All users</CardTitle>
+          <CardDescription>
+            Promote a user to admin, demote them back, reset their
+            password, or delete the account. The last admin cannot be
+            demoted or deleted.
+          </CardDescription>
+        </CardHeader>
+        <CardContent className="space-y-3">
           {rows.map((u) => (
             <UserRowClient
               key={u.id}
               user={{
                 id: u.id,
                 username: u.username,
-                role: (u.role === "admin" ? "admin" : "user"),
+                role: u.role === "admin" ? "admin" : "user",
               }}
               isSelf={u.id === me.id}
+              isLastAdmin={u.role === "admin" && adminCount === 1}
             />
           ))}
         </CardContent>

apps/web/src/app/settings/users/user-row-client.tsx

@@ -1,9 +1,26 @@
 "use client";
 
 import { useState, useTransition } from "react";
-import { Loader2Icon, Trash2Icon, KeyIcon, ArrowUpDownIcon } from "lucide-react";
+import {
+  Loader2Icon,
+  Trash2Icon,
+  KeyIcon,
+  ArrowUpIcon,
+  ArrowDownIcon,
+} from "lucide-react";
+import { Badge } from "@/components/ui/badge";
 import { Button } from "@/components/ui/button";
 import { Input } from "@/components/ui/input";
+import {
+  Dialog,
+  DialogContent,
+  DialogDescription,
+  DialogFooter,
+  DialogHeader,
+  DialogTitle,
+  DialogTrigger,
+  DialogClose,
+} from "@/components/ui/dialog";
 import {
   setUserRoleAction,
   resetUserPasswordAction,
@@ -13,13 +30,16 @@ import {
 interface UserRowClientProps {
   user: { id: string; username: string; role: "admin" | "user" };
   isSelf: boolean;
+  /** True when this row is the only remaining admin. Disables demote+delete. */
+  isLastAdmin: boolean;
 }
 
-export function UserRowClient({ user, isSelf }: UserRowClientProps) {
+export function UserRowClient({ user, isSelf, isLastAdmin }: UserRowClientProps) {
   const [pending, start] = useTransition();
   const [error, setError] = useState<string | null>(null);
   const [resetVisible, setResetVisible] = useState(false);
   const [resetPw, setResetPw] = useState("");
+  const [deleteOpen, setDeleteOpen] = useState(false);
 
   function run<T extends { ok: boolean; error?: string }>(promise: Promise<T>) {
     start(async () => {
@@ -29,30 +49,60 @@ export function UserRowClient({ user, isSelf }: UserRowClientProps) {
     });
   }
 
+  const isAdmin = user.role === "admin";
+  // The role-toggle button is disabled if:
+  //   - flipping yourself (admin self-demotion is rejected server-side too)
+  //   - this row is the last remaining admin and would become a user
+  const roleToggleDisabled = pending || isSelf || (isAdmin && isLastAdmin);
+  const deleteDisabled = pending || isSelf || isLastAdmin;
+
   return (
     <div className="flex flex-col gap-2 rounded-lg border p-3">
       <div className="flex items-center justify-between gap-2">
         <div className="min-w-0">
           <p className="text-sm font-medium truncate">{user.username}</p>
-          <p className="text-xs text-muted-foreground">{user.role}{isSelf && " · you"}</p>
+          <div className="flex items-center gap-1.5">
+            <Badge
+              variant="secondary"
+              className={
+                isAdmin
+                  ? "bg-emerald-500/15 text-emerald-700 dark:bg-emerald-500/20 dark:text-emerald-400 border-transparent"
+                  : "bg-slate-200/60 text-slate-600 dark:bg-slate-700/40 dark:text-slate-300 border-transparent"
+              }
+            >
+              {user.role}
+            </Badge>
+            {isSelf && (
+              <span className="text-xs text-muted-foreground">you</span>
+            )}
+            {isAdmin && isLastAdmin && (
+              <span className="text-xs text-muted-foreground">
+                · last admin
+              </span>
+            )}
+          </div>
         </div>
-        <div className="flex gap-1">
+        <div className="flex flex-wrap justify-end gap-1">
           <Button
             type="button"
             size="sm"
             variant="ghost"
-            disabled={pending || isSelf}
+            disabled={roleToggleDisabled}
             onClick={() =>
               run(
                 setUserRoleAction({
                   userId: user.id,
-                  role: user.role === "admin" ? "user" : "admin",
+                  role: isAdmin ? "user" : "admin",
                 }),
               )
             }
           >
-            <ArrowUpDownIcon className="size-3.5" />
-            {user.role === "admin" ? "Demote" : "Promote"}
+            {isAdmin ? (
+              <ArrowDownIcon className="size-3.5" />
+            ) : (
+              <ArrowUpIcon className="size-3.5" />
+            )}
+            {isAdmin ? "Demote" : "Promote"}
           </Button>
           <Button
             type="button"
@@ -64,16 +114,54 @@ export function UserRowClient({ user, isSelf }: UserRowClientProps) {
             <KeyIcon className="size-3.5" />
             Reset
           </Button>
-          <Button
-            type="button"
-            size="sm"
-            variant="ghost"
-            className="text-destructive"
-            disabled={pending || isSelf}
-            onClick={() => run(deleteUserAction({ userId: user.id }))}
-          >
-            {pending ? <Loader2Icon className="size-3.5 animate-spin" /> : <Trash2Icon className="size-3.5" />}
-          </Button>
+          <Dialog open={deleteOpen} onOpenChange={setDeleteOpen}>
+            <DialogTrigger asChild>
+              <Button
+                type="button"
+                size="sm"
+                variant="ghost"
+                className="text-destructive"
+                disabled={deleteDisabled}
+              >
+                <Trash2Icon className="size-3.5" />
+                Delete
+              </Button>
+            </DialogTrigger>
+            <DialogContent>
+              <DialogHeader>
+                <DialogTitle>Delete user @{user.username}?</DialogTitle>
+                <DialogDescription>
+                  This permanently removes the account. They will be
+                  signed out on their next request and cannot sign in
+                  again. This cannot be undone.
+                </DialogDescription>
+              </DialogHeader>
+              <DialogFooter showCloseButton>
+                <DialogClose asChild>
+                  <Button type="button" variant="ghost" size="sm">
+                    Cancel
+                  </Button>
+                </DialogClose>
+                <Button
+                  type="button"
+                  variant="destructive"
+                  size="sm"
+                  disabled={pending}
+                  onClick={() => {
+                    setDeleteOpen(false);
+                    run(deleteUserAction({ userId: user.id }));
+                  }}
+                >
+                  {pending ? (
+                    <Loader2Icon className="size-3.5 animate-spin" />
+                  ) : (
+                    <Trash2Icon className="size-3.5" />
+                  )}
+                  Delete user
+                </Button>
+              </DialogFooter>
+            </DialogContent>
+          </Dialog>
         </div>
       </div>
       {resetVisible && (
@@ -88,9 +176,14 @@ export function UserRowClient({ user, isSelf }: UserRowClientProps) {
           <Button
             type="button"
             size="sm"
-            disabled={pending}
+            disabled={pending || resetPw.length < 10}
             onClick={() => {
-              run(resetUserPasswordAction({ userId: user.id, newPassword: resetPw }));
+              run(
+                resetUserPasswordAction({
+                  userId: user.id,
+                  newPassword: resetPw,
+                }),
+              );
               setResetPw("");
               setResetVisible(false);
             }}