Add banner and page explaining domain transition plans

frontend/lib/font_awesome_icons.js

@@ -6,6 +6,7 @@ import { faLinkedin } from '@fortawesome/free-brands-svg-icons/faLinkedin';
 import { faMagnifyingGlass } from '@fortawesome/free-solid-svg-icons/faMagnifyingGlass';
 import { faSquareFacebook } from '@fortawesome/free-brands-svg-icons/faSquareFacebook';
 import { faThreads } from '@fortawesome/free-brands-svg-icons/faThreads';
+import { faTriangleExclamation } from '@fortawesome/free-solid-svg-icons/faTriangleExclamation';
 import { faXTwitter } from '@fortawesome/free-brands-svg-icons/faXTwitter';
 import { faXmark } from '@fortawesome/free-solid-svg-icons/faXmark';
 import { faYoutube } from '@fortawesome/free-brands-svg-icons/faYoutube';
@@ -20,6 +21,7 @@ library.add(
   faMagnifyingGlass,
   faSquareFacebook,
   faThreads,
+  faTriangleExclamation,
   faXTwitter,
   faXmark,
   faYoutube,

source/docs/nlr-domain-transition.html.md

@@ -0,0 +1,16 @@
+---
+title: NLR.gov Domain Transition
+hidden_child: true
+---
+
+# NLR.gov Domain Transition
+
+The National Laboratory of the Rockies (NLR) is retiring the `nrel.gov` domain near the end of May and transitioning to the new `nlr.gov` domain.
+
+**To avoid an interruption in service, you need to update your API calls to use the new `developer.nlr.gov` URLs by April 30, 2026**, or by May 29, 2026, with short outages scheduled in May before the old domain expires. Your existing API key will continue to work—only the domain in the URL needs to be updated.
+
+Here is a timeline for this domain change:
+
+- **March 2, 2026:** The new `developer.nlr.gov` domain is available now to use and begin switching API calls to the new URLs.
+- **May 1, 2026:** Periodic brownouts (scheduled outages for short durations) will begin where traffic to the old `developer.nrel.gov` domain will return errors with instructions about using the new domain. Traffic already switched to the new `developer.nlr.gov` domain will not be affected.
+- **May 29, 2026:** The `developer.nrel.gov` domain will expire and stop working completely. DNS for the `nrel.gov` domain and all subdomains will cease to resolve and will not redirect.

source/layouts/layout.erb

@@ -34,6 +34,13 @@
     <main id="content" class="container-xl">
       <%= partial("layouts/breadcrumbs") %>
 
+      <div class="alert alert-warning d-flex align-items-center" role="alert">
+        <i class="fa-solid fa-triangle-exclamation bi flex-shrink-0 me-2"></i>
+        <p class="m-0 lh-sm">
+        <strong>Existing API users:</strong> Update any <code>developer.nrel.gov</code> references in your code to <code>developer.nlr.gov</code> by <strong>April 30, 2026</strong>, to avoid service interruptions. Learn more about the <%= link_to("domain transition", "/docs/nlr-domain-transition.html") %>.
+        </div>
+      </div>
+
       <%= yield %>
 
       <%= partial("layouts/edit_me") %>