Add v2 onboarding import contacts page and unify the onboarding v2 shell (#22212)

<img width="3024" height="1668" alt="CleanShot 2026-06-26 at 13 29
28@2x"
src="https://github.com/user-attachments/assets/9bdd0029-45eb-4ddb-859f-eaab9bb61406"
/>

Adds the new v2 onboarding **Import contacts** step (email + calendar
import), shown right after workspace creation in the v2 flow. The
presentational page was designed in a previous PR; this wires it in and
unifies the shell.

**What changed**
- Reuses and unifies the existing v2 onboarding shell: extracts
`OnboardingV2Layout` + `OnboardingV2Header` (the back + logo header, now
with the free-credits pill), and the `SignInUpV2` workspace-creation
step renders through it (old `SignInUpV2Header` removed).
- New `SyncEmailsV2` route (`/sync/emails-v2`) under `BlankLayout`,
wired to the same OAuth/skip hooks as v1 `SyncEmails`.
- The `SYNC_EMAIL` step routes to the new page only when
`isOnboardingV2` is set (mirrors the existing `WorkspaceActivation` →
`WorkspaceActivationV2` branch); the v1 modal is unchanged for the
non-v2 flow.
- No backend changes — reuses the `SYNC_EMAIL` status and
`skipSyncEmailOnboardingStep` mutation.

**Reviewer notes**
- Connect defaults to `METADATA` (private) visibility to match the "Only
you will be able to see your emails and events" note (v1 had a selector
defaulting to `SHARE_EVERYTHING`).
- The header free-credits pill shows `0` for now (no current-workspace
credits source on the frontend yet).
- The back button is hidden on the import page (no meaningful "back"
after workspace creation); unchanged on the workspace-creation step.

packages/twenty-front/src/testing/constants/UntestedAppPaths.ts

@@ -4,4 +4,5 @@ export const UNTESTED_APP_PATHS = [
   AppPath.Settings,
   AppPath.Developers,
   AppPath.WorkspaceActivationV2,
+  AppPath.SyncEmailsV2,
 ];