[Announcement] Migration to apache/paimon-cpp

### Search before asking

- [x] I searched in the [issues](https://github.com/alibaba/paimon-cpp/issues) and found nothing similar.

### Motivation

We are excited to announce that **Apache Paimon C++** is migrating to its official Apache repository:

👉 https://github.com/apache/paimon-cpp

### Solution

### Migration Plan

- We plan to migrate starting from the **release-0.2** milestone.
- During the transition, active development continues at https://github.com/alibaba/paimon-cpp. Once release-0.2 is stable and fully migrated, subsequent PRs will be moved to `apache/paimon-cpp`.

### Large, Independent Features (e.g., Range Index, System Table)

For contributors working on larger self-contained features, we offer two options:

1. **We migrate on your behalf** — We will port your PR to the new repository.
2. **You migrate it yourself** — You can resubmit your PR directly to `apache/paimon-cpp` once all prerequisite dependencies are ready.

If you prefer option 2, we will @mention you at the appropriate time to proceed with the migration.

Please let us know your preference in the comments.

### What's Next

Once migration is complete, all future contributions should target https://github.com/apache/paimon-cpp.

We will keep this issue updated with progress.

---

Thank you for your continued support! We look forward to seeing you on the new repository.

### Anything else?

_No response_

### Are you willing to submit a PR?

- [x] I'm willing to submit a PR!