Add entity customer numbers and scope APIs via selected company.

Entity gets an optional unique-per-company number with allocate/peek/isNumberFree helpers. Company-scoped store methods no longer take companyId and resolve google_auth.selected_company instead.

API.article.md

@@ -80,7 +80,7 @@ Returns articles for export, optionally scoped to a category, including category
 
 ```js
 const fn = listExport(pool);
-const articles = await fn(42, 1, null);
+const articles = await fn(42, null);
 // => [{ id, sku, name, slug, unitSi, net, taxRate, eans, categoryBreadcrumbs, fullHashes, ... }]
 ```
 
@@ -92,7 +92,7 @@ Returns a lightweight search index of all articles for a company.
 
 ```js
 const fn = listSearchIndex(pool);
-const articles = await fn(42, 1);
+const articles = await fn(42);
 // => [{ id, sku, name, eans, categoryIds }]
 ```