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

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

superset-frontend/plugins/plugin-chart-table/src/index.ts

@@ -19,9 +19,13 @@
 import { Behavior, ChartMetadata, ChartPlugin, t } from '@superset-ui/core';
 import transformProps from './transformProps';
 import thumbnail from './images/thumbnail.png';
+import thumbnailDark from './images/thumbnail-dark.png';
 import example1 from './images/Table.jpg';
+import example1Dark from './images/Table-dark.jpg';
 import example2 from './images/Table2.jpg';
+import example2Dark from './images/Table2-dark.jpg';
 import example3 from './images/Table3.jpg';
+import example3Dark from './images/Table3-dark.jpg';
 import controlPanel from './controlPanel';
 import buildQuery from './buildQuery';
 import { TableChartFormData, TableChartProps } from './types';
@@ -41,7 +45,11 @@ const metadata = new ChartMetadata({
   description: t(
     'Classic row-by-column spreadsheet like view of a dataset. Use tables to showcase a view into the underlying data or to show aggregated metrics.',
   ),
-  exampleGallery: [{ url: example1 }, { url: example2 }, { url: example3 }],
+  exampleGallery: [
+    { url: example1, urlDark: example1Dark },
+    { url: example2, urlDark: example2Dark },
+    { url: example3, urlDark: example3Dark },
+  ],
   name: t('Table'),
   tags: [
     t('Additive'),
@@ -53,6 +61,7 @@ const metadata = new ChartMetadata({
     t('Tabular'),
   ],
   thumbnail,
+  thumbnailDark,
 });
 
 export default class TableChartPlugin extends ChartPlugin<