feat(docs): Docusaurus multi-versioning, Developer Portal starter kit (#34271)

Co-authored-by: Claude <noreply@anthropic.com>

docs/src/theme/DocVersionBanner/styles.module.css

@@ -0,0 +1,49 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+.versionBanner {
+  background-color: var(--ifm-color-emphasis-100);
+  padding: 0.5rem 1rem;
+  margin-bottom: 1rem;
+  border-bottom: 1px solid var(--ifm-color-emphasis-200);
+}
+
+.versionContainer {
+  display: flex;
+  align-items: center;
+  max-width: var(--ifm-container-width);
+  margin: 0 auto;
+  padding: 0 var(--ifm-spacing-horizontal);
+}
+
+.versionLabel {
+  font-weight: bold;
+  margin-right: 0.5rem;
+}
+
+.versionSelector {
+  cursor: pointer;
+  color: var(--ifm-color-primary);
+  font-weight: 500;
+}
+
+.versionSelector:hover {
+  text-decoration: none;
+  color: var(--ifm-color-primary-darker);
+}