legacy-final: Final version from the original author

This tag marks the last commit maintained by the original author @shd101wyy (0xGG team). The project's backend service (the crossnote.app GraphQL API) had already been shut down before this point; the frontend still works as a local-first PWA.

From here on the project is maintained by @dongshunyao and undergoes a complete rebuild. The pre-handover history is preserved on the archive/develop branch.