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.

docs/api/routes/entity/next-number.md

@@ -0,0 +1,32 @@
+# `GET /entity/next-number`
+
+Protected. Requires a valid session cookie (`credentials: 'include'`).
+
+Peek next customer number
+
+Returns the next customer number that would be allocated (`type` entity)
+without consuming it. Use on the customer add form.
+
+
+## Response `200`
+
+Next number
+
+```json
+{
+  "number": "…"
+}
+```
+
+## Errors
+
+| Status | Description |
+|--------|-------------|
+| 400 | No company selected — `{"error":"…"}` |
+| 401 | Unauthorized — `{"error":"…"}` |
+| 403 | Not authorized — `{"error":"…"}` |
+| 404 | Company not found — `{"error":"…"}` |
+
+---
+
+_Generated from `@openapi` JSDoc. Do not edit by hand — run `npm run docs:api`._