fix(FN-1704): use approved mobile breakpoint value (640px instead of 600px)

- Change @media query breakpoint from 600px to 640px for .onboarding-resume-card
- 640px is an approved breakpoint value per mobile CSS guidelines
- Fixes mobile-css test failure that was blocking the build

packages/dashboard/app/styles.css

@@ -23231,7 +23231,7 @@ html .column.drag-over * {
   outline-offset: 2px;
 }
 
-@media (max-width: 600px) {
+@media (max-width: 640px) {
   .onboarding-resume-card {
     flex-direction: column;
     align-items: stretch;