Add article.setPricesBySku to replace POS prices for a SKU.

Gives dashback a single store call that atomically replaces all price rows for the article’s poscustomergroup.

src/sql/price.js

@@ -0,0 +1,11 @@
+export const DELETE_BY_ARTICLE_AND_CUSTOMERGROUP = `
+DELETE FROM price
+WHERE article_id = @articleId
+  AND customergroup_id = @customerGroupId
+`;
+
+export const CREATE = `
+INSERT INTO price (tax_id, article_id, minmultiplier, customergroup_id, net)
+OUTPUT INSERTED.id
+VALUES (@taxId, @articleId, @minmultiplier, @customerGroupId, @net)
+`;