refactor(config): move storybook and vitest configs to config/, import app.css in storybook preview

config/storybook/preview.ts

@@ -0,0 +1,22 @@
+import '../../src/app/styles/app.css';
+import type { Preview } from '@storybook/sveltekit'
+
+const preview: Preview = {
+  parameters: {
+    controls: {
+      matchers: {
+       color: /(background|color)$/i,
+       date: /Date$/i,
+      },
+    },
+
+    a11y: {
+      // 'todo' - show a11y violations in the test UI only
+      // 'error' - fail CI on a11y violations
+      // 'off' - skip a11y checks entirely
+      test: 'todo'
+    }
+  },
+};
+
+export default preview;