refactor: restyle login page with UI components

Improves the login page's visual appearance by using Card and Input components.

src/components/ui/input.tsx

@@ -0,0 +1,21 @@
+import * as React from 'react';
+
+import { cn } from '@/lib/utils';
+
+function Input({ className, type, ...props }: React.ComponentProps<'input'>) {
+  return (
+    <input
+      type={type}
+      data-slot='input'
+      className={cn(
+        'file:text-foreground placeholder:text-muted-foreground selection:bg-primary selection:text-primary-foreground dark:bg-input/30 border-input flex h-9 w-full min-w-0 rounded-md border bg-transparent px-3 py-1 text-base shadow-xs transition-[color,box-shadow] outline-none file:inline-flex file:h-7 file:border-0 file:bg-transparent file:text-sm file:font-medium disabled:pointer-events-none disabled:cursor-not-allowed disabled:opacity-50 md:text-sm',
+        'focus-visible:border-ring focus-visible:ring-ring/50 focus-visible:ring-[3px]',
+        'aria-invalid:ring-destructive/20 dark:aria-invalid:ring-destructive/40 aria-invalid:border-destructive',
+        className,
+      )}
+      {...props}
+    />
+  );
+}
+
+export { Input };