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/components/ui/card.tsx

@@ -0,0 +1,103 @@
+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

@@ -0,0 +1,20 @@
+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

@@ -0,0 +1,18 @@
+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 }