Add customergroup and entity HTTP APIs with address and contact routes.

Expose store-backed CRUD for customer groups, entities, nested addresses, and contacts, matching the documented dashdbschema contracts.

docs/api/routes/entity/delete.md

@@ -0,0 +1,32 @@
+# `DELETE /entity/{id}`
+
+Protected. Requires a valid session cookie (`credentials: 'include'`).
+
+Delete entity
+
+Deletes the entity (`entityhistory` cascades; related addresses/contacts cascade).
+
+## Path parameters
+
+| Param | Required | Type | Description |
+|-------|----------|------|-------------|
+| `id` | yes | integer |  |
+
+## Response `204`
+
+Deleted
+
+_No content_
+
+## Errors
+
+| Status | Description |
+|--------|-------------|
+| 400 | No company selected or invalid id — `{"error":"…"}` |
+| 401 | Unauthorized — `{"error":"…"}` |
+| 403 | Not authorized — `{"error":"…"}` |
+| 404 | Entity not found — `{"error":"…"}` |
+
+---
+
+_Generated from `@openapi` JSDoc. Do not edit by hand — run `npm run docs:api`._