Fix signup visual regression in workspace selection layout (#22965)

## Summary
- Split the sign-in/up onboarding container styles so workspace
selection can keep its wider layout without affecting the other auth
states.
- Reuse the base onboarding container for the non-selection flow to
restore the intended visual structure.


https://github.com/twentyhq/twenty/commit/566c3b662954de932677a3fefe69735a45fe55ae
commit accidentally reused the 440px workspace-selection container for
the global credential form

## Before
<img width="643" height="496" alt="Screenshot 2026-07-16 at 18 14 35"
src="https://github.com/user-attachments/assets/abff0779-a236-424f-9503-9182dab5fa3f"
/>

## After
<img width="510" height="509" alt="Screenshot 2026-07-16 at 18 11 58"
src="https://github.com/user-attachments/assets/8c4693b2-827f-4bc8-a9ce-10171bbb7d0b"
/>


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

@@ -38,7 +38,9 @@ import {
 import { getWorkspaceUrl } from '~/utils/getWorkspaceUrl';
 import { getAbsoluteImageUrl } from '~/utils/image/getAbsoluteImageUrl';
 
-const StyledContentContainer = styled(StyledOnboardingContentContainer)`
+const StyledWorkspaceSelectionContentContainer = styled(
+  StyledOnboardingContentContainer,
+)`
   max-width: 100%;
   width: ${ONBOARDING_CONTENT_BLOCK_WIDTH}px;
 `;
@@ -171,7 +173,7 @@ export const SignInUpGlobalScopeForm = () => {
   return (
     <>
       {signInUpStep === SignInUpStep.WorkspaceSelection && (
-        <StyledContentContainer>
+        <StyledWorkspaceSelectionContentContainer>
           <StyledWorkspaceContainer>
             {availableWorkspacesList.map((availableWorkspace, index) => (
               <OnboardingStepAnimatedItem
@@ -235,10 +237,10 @@ export const SignInUpGlobalScopeForm = () => {
               </OnboardingStepAnimatedItem>
             )}
           </StyledWorkspaceContainer>
-        </StyledContentContainer>
+        </StyledWorkspaceSelectionContentContainer>
       )}
       {signInUpStep !== SignInUpStep.WorkspaceSelection && (
-        <StyledContentContainer>
+        <StyledOnboardingContentContainer>
           {authProviders.google && (
             <SignInUpWithGoogle
               action="list-available-workspaces"
@@ -269,7 +271,7 @@ export const SignInUpGlobalScopeForm = () => {
               </ClickToActionLink>
             </StyledForgotPasswordLinkContainer>
           )}
-        </StyledContentContainer>
+        </StyledOnboardingContentContainer>
       )}
     </>
   );