Add Playwright e2e coverage and Node 20 pin

frontend/src/pages/LoginPage.tsx

@@ -86,7 +86,7 @@ export function LoginPage() {
           </p>
         </div>
 
-        <form onSubmit={handleSubmit} className="mt-8 space-y-6">
+        <form onSubmit={handleSubmit} className="mt-8 space-y-6" data-testid="login-form">
           <div className="glass-card-static p-6 space-y-4">
             {(error || localError) && (
               <div className="rounded-[10px] border border-rose-500/20 bg-rose-500/10 p-3 text-sm text-rose-400">
@@ -146,6 +146,7 @@ export function LoginPage() {
             <button
               type="submit"
               disabled={isLoading}
+              data-testid="login-submit"
               className={cn(
                 'w-full rounded-[10px] px-4 py-2.5 text-sm font-semibold',
                 'bg-gradient-brand text-brand-dark shadow-lg shadow-primary/20 hover:opacity-90 active:scale-[0.97]',