feat: Implement dark/light mode toggle and address linting issues

This commit introduces a functional dark/light mode toggle by integrating
`next-themes` with the application. It configures `ThemeProvider` in
`src/frontend.tsx` and sets `darkMode: 'class'` in `tailwind.config.js`.

Additionally, this commit resolves several linting and parsing issues
found in `src/index.ts`.

This commit also includes other pre-existing modifications and new
components within the project's working directory that were not
specifically part of the dark mode or linting tasks.

src/components/ui/slider.tsx

@@ -1,7 +1,7 @@
 "use client";
 
-import * as React from "react";
 import * as SliderPrimitive from "@radix-ui/react-slider";
+import * as React from "react";
 import { ulid } from "ulid";
 
 import { cn } from "./utils"; // Assuming cn is used and imported from ./utils