Revert "Update CURATION_GITHUB_CLIENT_ID for 'devtree'"

This reverts commit 40da672b664ce656b421a91aaaad111e10ec5712.
Revert "Rename and cleanup GitHub client-ID vars"

This reverts commit 26a2c0bf2e2641b89bfe7b0f1bc00ee435a27455.
Revert "Update public-facing domain 'dev' => 'devtree'"

This reverts commit 7a79044fed8c2094f81fb32c69a53b9c9f99307b.