add a temporary notice banner to the layout (#7217)

app/layout/index.jsx

@@ -10,6 +10,45 @@ export default function AppLayout(props) {
         <div className="app-layout__admin-indicator" title="Admin mode on!" />
       </AdminOnly>
 
+      <details
+          style={{
+            padding: '5px clamp(20px, 3vw, 30px)',
+            fontSize: '1rem',
+            lineHeight: 1.2,
+            color: '#000',
+            background: '#f0b200'
+          }}
+        >
+          <summary style={{ fontWeight: 'bold', cursor: 'pointer' }}>
+            Platform downtime scheduled on Wednesday November 20.
+          </summary>
+          <p style={{ paddingInline: '15px' }}>
+            The Zooniverse platform will be offline for scheduled maintenance on
+            Wednesday, November 20 from 4pm-10pm US Central Standard Time
+            (2024-11-20 22:00 UTC to 2024-11-21 4:00 UTC). During this period, all
+            projects and platform services will be inaccessible. We apologize for
+            the inconvenience; this maintenance is necessary to make updates to
+            platform infrastructure and improve long-term reliability and uptime.
+            Please visit{' '}
+            <a
+              href='https://status.zooniverse.org/incident/1019747'
+              target='_blank'
+              style={{ color: '#000' }}
+            >
+              status.zooniverse.org
+            </a>{' '}
+            for updates before and during the downtime period. For any additional
+            questions, please email{' '}
+            <a
+              style={{ color: '#000' }}
+              href='mailto:[email protected]'
+            >
+              [email protected]
+            </a>
+            .
+          </p>
+        </details>
+
       <header className='app-layout__header'>
         <SiteNav params={props.params} />
       </header>