feat(web): login page with inline error handling

Add shadcn input/label/card primitives and implement the login page:
email/password form using useLogin, navigates to /objects on success,
shows inline i18n error on 401 (auth.invalid) or network failure.
2 new tests, 9 total green.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web/src/auth/login-page.test.tsx

@@ -0,0 +1,36 @@
+import { expect, test } from "vitest";
+import { screen, waitFor } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { http, HttpResponse } from "msw";
+import { Routes, Route } from "react-router-dom";
+import { server } from "../test/server";
+import { renderApp } from "../test/render";
+import { LoginPage } from "./login-page";
+
+function tree() {
+  return (
+    <Routes>
+      <Route path="/login" element={<LoginPage />} />
+      <Route path="/objects" element={<div>objects landing</div>} />
+    </Routes>
+  );
+}
+
+test("successful login navigates to /objects", async () => {
+  renderApp(tree(), { route: "/login" });
+  await userEvent.type(screen.getByLabelText(/email/i), "editor@example.com");
+  await userEvent.type(screen.getByLabelText(/password/i), "pw-editor-123");
+  await userEvent.click(screen.getByRole("button", { name: /sign in/i }));
+  expect(await screen.findByText("objects landing")).toBeInTheDocument();
+});
+
+test("invalid credentials show an inline error", async () => {
+  server.use(http.post("/api/admin/login", () => new HttpResponse(null, { status: 401 })));
+  renderApp(tree(), { route: "/login" });
+  await userEvent.type(screen.getByLabelText(/email/i), "x@y.se");
+  await userEvent.type(screen.getByLabelText(/password/i), "wrong");
+  await userEvent.click(screen.getByRole("button", { name: /sign in/i }));
+  await waitFor(() =>
+    expect(screen.getByText(/invalid email or password/i)).toBeInTheDocument(),
+  );
+});

web/src/auth/login-page.tsx

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+import { useState, type FormEvent } from "react";
+import { useNavigate } from "react-router-dom";
+import { useTranslation } from "react-i18next";
+
+import { useLogin } from "../api/queries";
+import { Button } from "@/components/ui/button";
+import { Input } from "@/components/ui/input";
+import { Label } from "@/components/ui/label";
+
+export function LoginPage() {
+  const { t } = useTranslation();
+  const navigate = useNavigate();
+  const login = useLogin();
+  const [email, setEmail] = useState("");
+  const [password, setPassword] = useState("");
+
+  const onSubmit = (event: FormEvent) => {
+    event.preventDefault();
+    login.mutate(
+      { email, password },
+      { onSuccess: () => navigate("/objects", { replace: true }) },
+    );
+  };
+
+  const errorKey = login.error
+    ? login.error.message === "invalid"
+      ? "auth.invalid"
+      : "auth.networkError"
+    : null;
+
+  return (
+    <div className="flex min-h-screen items-center justify-center p-4">
+      <form onSubmit={onSubmit} className="w-full max-w-sm space-y-4">
+        <h1 className="text-2xl font-semibold">{t("app.name")}</h1>
+        <div className="space-y-2">
+          <Label htmlFor="email">{t("auth.email")}</Label>
+          <Input
+            id="email"
+            type="email"
+            value={email}
+            onChange={(event) => setEmail(event.target.value)}
+            autoComplete="username"
+          />
+        </div>
+        <div className="space-y-2">
+          <Label htmlFor="password">{t("auth.password")}</Label>
+          <Input
+            id="password"
+            type="password"
+            value={password}
+            onChange={(event) => setPassword(event.target.value)}
+            autoComplete="current-password"
+          />
+        </div>
+        {errorKey && (
+          <p role="alert" className="text-sm text-red-600">
+            {t(errorKey)}
+          </p>
+        )}
+        <Button type="submit" className="w-full" disabled={login.isPending}>
+          {t("auth.signIn")}
+        </Button>
+      </form>
+    </div>
+  );
+}

web/src/components/ui/card.tsx

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+import * as React from "react"
+
+import { cn } from "@/lib/utils"
+
+function Card({
+  className,
+  size = "default",
+  ...props
+}: React.ComponentProps<"div"> & { size?: "default" | "sm" }) {
+  return (
+    <div
+      data-slot="card"
+      data-size={size}
+      className={cn(
+        "group/card flex flex-col gap-4 overflow-hidden rounded-xl bg-card py-4 text-sm text-card-foreground ring-1 ring-foreground/10 has-data-[slot=card-footer]:pb-0 has-[>img:first-child]:pt-0 data-[size=sm]:gap-3 data-[size=sm]:py-3 data-[size=sm]:has-data-[slot=card-footer]:pb-0 *:[img:first-child]:rounded-t-xl *:[img:last-child]:rounded-b-xl",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+function CardHeader({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="card-header"
+      className={cn(
+        "group/card-header @container/card-header grid auto-rows-min items-start gap-1 rounded-t-xl px-4 group-data-[size=sm]/card:px-3 has-data-[slot=card-action]:grid-cols-[1fr_auto] has-data-[slot=card-description]:grid-rows-[auto_auto] [.border-b]:pb-4 group-data-[size=sm]/card:[.border-b]:pb-3",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+function CardTitle({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="card-title"
+      className={cn(
+        "text-base leading-snug font-medium group-data-[size=sm]/card:text-sm",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+function CardDescription({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="card-description"
+      className={cn("text-sm text-muted-foreground", className)}
+      {...props}
+    />
+  )
+}
+
+function CardAction({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="card-action"
+      className={cn(
+        "col-start-2 row-span-2 row-start-1 self-start justify-self-end",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+function CardContent({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="card-content"
+      className={cn("px-4 group-data-[size=sm]/card:px-3", className)}
+      {...props}
+    />
+  )
+}
+
+function CardFooter({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="card-footer"
+      className={cn(
+        "flex items-center rounded-b-xl border-t bg-muted/50 p-4 group-data-[size=sm]/card:p-3",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+export {
+  Card,
+  CardHeader,
+  CardFooter,
+  CardTitle,
+  CardAction,
+  CardDescription,
+  CardContent,
+}

web/src/components/ui/input.tsx

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+import * as React from "react"
+import { Input as InputPrimitive } from "@base-ui/react/input"
+
+import { cn } from "@/lib/utils"
+
+function Input({ className, type, ...props }: React.ComponentProps<"input">) {
+  return (
+    <InputPrimitive
+      type={type}
+      data-slot="input"
+      className={cn(
+        "h-8 w-full min-w-0 rounded-lg border border-input bg-transparent px-2.5 py-1 text-base transition-colors outline-none file:inline-flex file:h-6 file:border-0 file:bg-transparent file:text-sm file:font-medium file:text-foreground placeholder:text-muted-foreground focus-visible:border-ring focus-visible:ring-3 focus-visible:ring-ring/50 disabled:pointer-events-none disabled:cursor-not-allowed disabled:bg-input/50 disabled:opacity-50 aria-invalid:border-destructive aria-invalid:ring-3 aria-invalid:ring-destructive/20 md:text-sm dark:bg-input/30 dark:disabled:bg-input/80 dark:aria-invalid:border-destructive/50 dark:aria-invalid:ring-destructive/40",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+export { Input }

web/src/components/ui/label.tsx

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+import * as React from "react"
+
+import { cn } from "@/lib/utils"
+
+function Label({ className, ...props }: React.ComponentProps<"label">) {
+  return (
+    <label
+      data-slot="label"
+      className={cn(
+        "flex items-center gap-2 text-sm leading-none font-medium select-none group-data-[disabled=true]:pointer-events-none group-data-[disabled=true]:opacity-50 peer-disabled:cursor-not-allowed peer-disabled:opacity-50",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+export { Label }