fix(a11y): announce form-level errors via role=alert in Login + ResetPassword

Wrap the error message blocks in role=alert so assistive technology announces
authentication failures and reset-password errors when they appear (WCAG 4.1.3).

src/pages/ResetPassword.tsx

@@ -149,7 +149,10 @@ export default function ResetPassword() {
                 </div>
 
                 {error && (
-                  <div className="rounded-xl border border-error-500/30 bg-error-500/10 px-4 py-3 text-sm text-error-400">
+                  <div
+                    role="alert"
+                    className="rounded-xl border border-error-500/30 bg-error-500/10 px-4 py-3 text-sm text-error-400"
+                  >
                     {error}
                   </div>
                 )}