Align store calls with selected-company scoping and add entity numbers.

Drop companyId from company-scoped store wrappers and routes, add GET /entity/next-number plus optional number on entity create/update, and document dashdbschema API.md lookup in sibling-repos.

src/api/routes/pic.js

@@ -13,6 +13,7 @@ function parseFullHash(value) {
 }
 
 function picErrorStatus(error) {
+    if (error.message === 'No company selected') return 400;
     if (error.message === 'Not authorized') return 403;
     if (error.message === 'Image not found') return 404;
     return 500;