API client, auth bootstrap and job polling (#42)

Co-authored-by: dev_agent <dev_agent@cubecraftlabs.com>
Co-committed-by: dev_agent <dev_agent@cubecraftlabs.com>

web/src/pages/FullScreen.module.css

@@ -0,0 +1,23 @@
+/* A full-viewport screen shown instead of the app shell. */
+.screen {
+  min-height: 100dvh;
+  display: flex;
+  flex-direction: column;
+  justify-content: center;
+  gap: var(--space-3);
+  padding: var(--space-8) var(--space-4);
+  background: var(--color-bg);
+}
+
+.loading {
+  width: min(100%, 480px);
+  margin: 0 auto;
+  display: flex;
+  flex-direction: column;
+  gap: var(--space-3);
+}
+
+.title {
+  height: 32px;
+  width: 60%;
+}

web/src/pages/NotInHouseholdPage.tsx

@@ -0,0 +1,14 @@
+import { EmptyState } from '../ui/EmptyState.tsx'
+import styles from './FullScreen.module.css'
+
+// Shown when the server refuses a signed-in account that is not in this
+// household. Nothing else renders: the account can do nothing here.
+export function NotInHouseholdPage() {
+  return (
+    <main className={styles.screen}>
+      <EmptyState title="Not in this household">
+        You are signed in, but this account is not in this household. Ask someone in Our kitchen to add it.
+      </EmptyState>
+    </main>
+  )
+}