Phase 1 of the parent/child rollup feature. Self-FK on properties
with ON DELETE RESTRICT, plus a CHECK that blocks self-reference at
the DB level. Service-layer helpers (getDescendantIds,
getAncestorIds, assertNoCycle) walk the tree via recursive CTEs and
guard against cycles and cross-company parents. softDeleteProperty
now refuses to delete a property with live children.
No UI yet — readers and roll-up routes land in Phase 2.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
