Add company-scoped unit list/upsert/delete and article unit patches.

Units are isolated per company; article detail exposes full unit shape, and unused units can be deleted safely via FK NO ACTION.

src/store/article/createUnderParent.js

@@ -28,7 +28,7 @@ export default function createUnderParent(pool) {
     await tx.begin();
 
     try {
-      const unitId = await ensureUnit(tx);
+      const unitId = await ensureUnit(tx, languageId, companyId);
       const sku = await allocateSku(companyId, tx);
       const slug = slugify(name);