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/index.css

@@ -1,24 +1 @@
-@import "tailwindcss";
-
-:root {
-	font-family: Inter, system-ui, Avenir, Helvetica, Arial, sans-serif;
-	line-height: 1.5;
-	font-weight: 400;
-
-	color-scheme: light dark;
-	color: rgba(255, 255, 255, 0.87);
-	background-color: #242424;
-
-	font-synthesis: none;
-	text-rendering: optimizeLegibility;
-	-webkit-font-smoothing: antialiased;
-	-moz-osx-font-smoothing: grayscale;
-}
-
-body {
-	margin: 0;
-	display: flex;
-	place-items: center;
-	min-width: 320px;
-	min-height: 100vh;
-}
+@import "tailwindcss";