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.

tailwind.config.js

@@ -1,5 +1,6 @@
 /** @type {import('tailwindcss').Config} */
 module.exports = {
+	darkMode: "class",
 	content: ["./index.html", "./src/**/*.{js,ts,jsx,tsx}"],
 	theme: {
 		extend: {