Update for darkmode and some bug fixes.

Author: cyber937

.storybook/preview.ts

@@ -0,0 +1,43 @@
+import type { Preview } from "@storybook/react-vite";
+import "../src/index.css";
+
+const preview: Preview = {
+  parameters: {
+    backgrounds: {
+      options: {
+        light: { name: "light", value: "#F7F9F2" }, // ライトテーマ用背景
+        dark: { name: "dark", value: "#333" }, // ダークテーマ用背景
+      },
+    },
+    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",
+    },
+  },
+  decorators: [
+    (Story, context) => {
+      const isDark = context.globals.backgrounds?.value === "dark";
+      const html = document.documentElement;
+      if (isDark) {
+        html.classList.add("dark");
+      } else {
+        html.classList.remove("dark");
+      }
+      return <Story />;
+    },
+  ],
+  initialGlobals: {
+    backgrounds: { value: "light" },
+  },
+};
+
+export default preview;