Add v2 onboarding loading screen while creating workspace (#22152)

https://github.com/user-attachments/assets/cc7b1d10-7495-4f21-9311-4c22c0f14771

Adds the full-screen loading screen shown while a new workspace is being
created in the v2 sign-up flow (`SignInUpV2`), building on the v2
"Create your workspace" step.

How it works:
- Submitting the v2 create-workspace form marks the flow as v2
(`isOnboardingV2State`) and creates the workspace. The flag is carried
across the cross-subdomain redirect with an `onboardingV2=true` URL
param, so v2 users land on a new `/workspace-activation-v2` route
instead of v1's `/workspace-activation`.
- `WorkspaceActivationV2` runs the real `activateWorkspace` mutation on
mount and renders the loader: a pulsing Twenty logomark above a stack of
status messages that shift up one at a time, cycling once per second.
There is no faked/minimum duration; it advances to the next onboarding
step as soon as the workspace is activated.
- On activation failure it shows a "Workspace creation failed" screen
with a Retry button.

v1 onboarding is unchanged. Storybook:
`Modules/Auth/SignInUpWorkspaceActivationV2`.

Note: The flashes will be fixed in later PRs

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packages/twenty-front/src/modules/app/hooks/useInitializeQueryParamState.ts

@@ -1,6 +1,7 @@
 import { useCallback } from 'react';
 
 import { billingCheckoutSessionState } from '@/auth/states/billingCheckoutSessionState';
+import { isOnboardingV2State } from '@/auth/states/isOnboardingV2State';
 import { returnToPathState } from '@/auth/states/returnToPathState';
 import { type BillingCheckoutSession } from '@/auth/types/billingCheckoutSession.type';
 import { isValidReturnToPath } from '@/auth/utils/isValidReturnToPath';
@@ -50,6 +51,11 @@ export const useInitializeQueryParamState = () => {
           store.set(returnToPathState.atom, value);
         }
       },
+      onboardingV2: (value: string) => {
+        if (value === 'true') {
+          store.set(isOnboardingV2State.atom, true);
+        }
+      },
     };
 
     const queryParams = new URLSearchParams(window.location.search);