feat: Add comprehensive dark mode support for chart thumbnails and examples (#35111)

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

superset-frontend/plugins/legacy-plugin-chart-partition/src/index.js

@@ -19,16 +19,19 @@
 import { t, ChartMetadata, ChartPlugin } from '@superset-ui/core';
 import transformProps from './transformProps';
 import thumbnail from './images/thumbnail.png';
+import thumbnailDark from './images/thumbnail-dark.png';
 import example from './images/example.jpg';
+import exampleDark from './images/example-dark.jpg';
 import controlPanel from './controlPanel';
 
 const metadata = new ChartMetadata({
   category: t('Part of a Whole'),
   description: t('Compare the same summarized metric across multiple groups.'),
-  exampleGallery: [{ url: example }],
+  exampleGallery: [{ url: example, urlDark: exampleDark }],
   name: t('Partition Chart'),
   tags: [t('Categorical'), t('Comparison'), t('Legacy'), t('Proportional')],
   thumbnail,
+  thumbnailDark,
   useLegacyApi: true,
 });