feat(ui): Improve login card design and theme customization

Refactor the `Button` component, add new `LoginCard` component, update `ThemePicker` component, edit global CSS styles to include card background and foreground and style the login page, including the logo and login form.

src/components/user/login-form.tsx

@@ -1,6 +1,6 @@
 import { signIn } from '@/auth';
 import LabeledInput from '@/components/labeled-input';
-import { Button } from '@/components/ui/button';
+import { Button } from '@/components/custom-ui/button';
 import { AuthError } from 'next-auth';
 import { redirect } from 'next/navigation';
 

src/components/user/redirect-button.tsx

@@ -1,4 +1,4 @@
-import { Button } from '../ui/button';
+import { Button } from '../custom-ui/button';
 import Link from 'next/link';
 
 export function RedirectButton({

src/components/user/sso-login-button.tsx

@@ -22,7 +22,6 @@ export default function SSOLogin({
         type='submit'
         variant='secondary'
         icon={faOpenid}
-        icon={faOpenid}
       >
         Login with {providerDisplayName}
       </IconButton>

src/components/user/theme-picker.tsx

@@ -4,7 +4,7 @@ import * as React from 'react';
 import { Moon, Sun } from 'lucide-react';
 import { useTheme } from 'next-themes';
 
-import { Button } from '@/components/ui/button';
+import { Button } from '@/components/custom-ui/button';
 import {
   DropdownMenu,
   DropdownMenuContent,