- Update migration count from 11 to 13 across all docs (012_bom_source,
013_move_cost_sourcing_to_props)
- Update endpoint count from 75 to 78 across all docs
- Add 3 missing endpoints to SPECIFICATION.md section 11.1:
GET /api/events (SSE), GET /api/items/by-uuid/{uuid},
POST /api/items/{pn}/bom/merge
- Add migrations 012 and 013 to STATUS.md table
- Fix migration 010 description (sourcing_link and standard_cost moved
to revision properties in 013)