test: add comprehensive dashboard component tests

- Configure vitest with jsdom environment for React component testing
- Add comprehensive tests for TopQuestionsChart component (6 tests)
- Add comprehensive tests for TranscriptViewer component (7 tests)
- Mock all necessary dependencies (ReactMarkdown, shadcn/ui components)
- All 13 component tests passing successfully
- GeographicMap excluded due to react-leaflet test environment issues

vitest.config.mts

@@ -5,7 +5,7 @@ import tsconfigPaths from "vite-tsconfig-paths";
 export default defineConfig({
   plugins: [tsconfigPaths(), react()],
   test: {
-    environment: "node",
+    environment: "jsdom",
     globals: true,
     setupFiles: ["./tests/setup.ts"],
     include: ["tests/**/*.{test,spec}.{js,mjs,cjs,ts,mts,cts,jsx,tsx}"],