OpenSEO now prevents duplicate auto-created Default projects per organization.

## Migration Note

Most installs do not need manual cleanup. If running the latest migrations fails
with a unique-constraint error for
`projects_one_default_per_organization_idx`, follow
`docs/default-project-cleanup.md`.

## What happened

Several simultaneous requests could initialize the same organization at once,
creating more than one auto-created `Default` project.

## What the cleanup does

The cleanup keeps one canonical `Default` project per organization, remaps
supported child rows onto it, preserves rank-tracking history where possible,
then removes duplicate Default projects.

Full Changelog: https://github.com/every-app/open-seo/compare/v0.0.13...v0.0.14
