fix: [ES Serverless home] Programming language options give no context to blind user (#188306)

Closes: https://github.com/elastic/search-team/issues/7618

# Description
A blind screen reader user receives no contextual information when
navigating through the list of programming languages.

# Steps to Reproduce
1. Open a `Search Serverless` project.
2. Navigate to the `Search` project homepage.

# Update Summary
Added the required `aria-label` attribute to the `LanguageGrid` select
button to provide context for screen reader users.

# Screen 

<img width="998" alt="image"
src="https://github.com/user-attachments/assets/e3b34cdc-7f57-46d9-93eb-83becd5ce6d0">

x-pack/plugins/serverless_search/public/application/components/languages/language_grid.tsx

@@ -18,6 +18,7 @@ import {
 } from '@elastic/eui';
 
 import { LanguageDefinition, Languages } from '@kbn/search-api-panels';
+import { i18n } from '@kbn/i18n';
 
 export interface LanguageGridProps {
   assetBasePath: string;
@@ -52,6 +53,15 @@ export const LanguageGrid: React.FC<LanguageGridProps> = ({
             onClick={() => setSelectedLanguage(language)}
             color={language.id === selectedLanguage ? 'primary' : 'plain'}
             data-test-subj={`${language.id}-client-panel`}
+            aria-label={i18n.translate(
+              'xpack.serverlessSearch.languageGrid.selectButton.ariaLabel',
+              {
+                defaultMessage: 'Select "{client}" client',
+                values: {
+                  client: language.id,
+                },
+              }
+            )}
           >
             <EuiFlexGroup justifyContent="flexStart" responsive={false}>
               <EuiFlexItem grow={false}>