Phase 3 of the sub-property hierarchy feature.
- New/edit forms grow a "Parent property" select. Edit-side options
exclude the current property and its descendants so the picker
itself can't create a cycle; service-layer assertNoCycle is the
belt-and-braces guard if a malicious form bypasses the dropdown.
- New form accepts ?parent=<id> as a preselect so "Add sub-property"
links from the parent's tab land in a pre-wired form.
- Property detail layout: breadcrumb (Parent › Child) when parent
is set, plus a new "Sub-properties (N)" tab.
- Dedicated Sub-properties tab lists direct children with a
+ New sub-property button.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
grabowski
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