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/unit/delete.js

@@ -0,0 +1,31 @@
+import { DELETE_BY_COMPANY_AND_SI } from '../../sql/unit.js';
+import resolveCompanyAccess from '../companyuser/resolveCompanyAccess.js';
+
+export default function del(pool) {
+  const access = resolveCompanyAccess(pool);
+
+  return async (googleAuthId, companyId, si) => {
+    if (!si?.trim()) {
+      throw new Error('Unit not found');
+    }
+
+    await access(googleAuthId, companyId);
+
+    try {
+      const result = await pool
+        .request()
+        .input('companyId', companyId)
+        .input('si', si.trim())
+        .query(DELETE_BY_COMPANY_AND_SI);
+
+      if (!result.rowsAffected[0]) {
+        throw new Error('Unit not found');
+      }
+    } catch (err) {
+      if (err.number === 547) {
+        throw new Error('Unit in use');
+      }
+      throw err;
+    }
+  };
+}