fix: replace remaining Plasmic references in page titles

[field123]

Summary

• Replace "Plasmic" with "Visual Builder" in dashboard page titles (page-utils.tsx via React Helmet)
• Replace "Redirecting to Plasmic..." with "Redirecting to Visual Builder..." in auth callback
• Replace "Plasmic Email Host" with "Visual Builder Email Host" in email host template

Files changed

• platform/wab/src/wab/client/components/dashboard/page-utils.tsx
• platform/wab/src/wab/server/auth/callback.html
• platform/wab/src/wab/server/emails/host/index.html

Test plan

• Open dashboard pages and verify browser tab shows "Visual Builder" instead of "Plasmic"
• Test auth flow and verify redirect page title