CN Quickstart card should link to internal page and not git repo

Link https://docs.canton.network/appdev/modules/m2-migration-checklist#next-steps.

<img width="793" height="213" alt="Image" src="https://github.com/user-attachments/assets/4a3258c3-aee6-474e-b0e1-65652d9b21fa" />