Make onboarding cards contrast with the page background (#23516)

Onboarding card surfaces used `background.secondary`, the same token as
the onboarding page background, so they blended in (visible on the
workspace selection step).

Switched them to `background.primary`, matching the other onboarding
cards (plan card, install apps, trust badges).

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packages/twenty-front/src/modules/auth/sign-in-up/components/SignInUpGlobalScopeForm.tsx

@@ -38,8 +38,8 @@ import { getWorkspaceUrl } from '~/utils/getWorkspaceUrl';
 import { getAbsoluteImageUrl } from '~/utils/image/getAbsoluteImageUrl';
 
 const StyledWorkspaceContainer = styled.div`
-  background-color: ${themeCssVariables.background.secondary};
-  border: 1px solid ${themeCssVariables.border.color.light};
+  background-color: ${themeCssVariables.background.primary};
+  border: 1px solid ${themeCssVariables.border.color.medium};
   border-radius: ${themeCssVariables.border.radius.md};
   display: flex;
   flex-direction: column;

packages/twenty-front/src/modules/onboarding/components/import-contacts/OnboardingImportPreview.tsx

@@ -10,7 +10,7 @@ const PREVIEW_HEIGHT = 198;
 
 const StyledCard = styled.div`
   align-items: center;
-  background-color: ${themeCssVariables.background.secondary};
+  background-color: ${themeCssVariables.background.primary};
   border: 1px solid ${themeCssVariables.border.color.medium};
   border-radius: 12px;
   box-sizing: border-box;