fix(core): mutations are non-transactional, leaving orphaned/partial data

[imhayatunnabi]

The Problem I have faced in bulk + large data operations:

create, update, delete and their *Many variants in packages/core/src/lib/core/mutations/index.ts write items
non-transactionally — there is no $transaction anywhere in the mutation path.
Because nested create inputs are persisted before the parent row is written,if the parent write then fails (a validate/beforeOperation hook, a DB constraint, etc.), the already-created related rows are left orphaned in the database with no rollback — the item ends up partially written.
For createMany / updateMany / deleteMany each item is committed independently, so a batch that fails partway leaves earlier items committed and later ones not.