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/contact/create.md

@@ -0,0 +1,50 @@
+# `POST /entity/{entityId}/contact`
+
+Protected. Requires a valid session cookie (`credentials: 'include'`).
+
+Create entity contact
+
+Creates a contact for the entity. `contactType` and `contact` are required.
+
+## Path parameters
+
+| Param | Required | Type | Description |
+|-------|----------|------|-------------|
+| `entityId` | yes | integer |  |
+
+## Body (JSON)
+
+```json
+{
+  "contactType": "email",
+  "contact": "anna@example.com"
+}
+```
+
+## Response `201`
+
+Created contact
+
+```json
+{
+  "contact": {
+    "id": 1,
+    "entityId": 1,
+    "contactType": "…",
+    "contact": "…"
+  }
+}
+```
+
+## Errors
+
+| Status | Description |
+|--------|-------------|
+| 400 | Contact required, invalid entityId, or no company selected — `{"error":"…"}` |
+| 401 | Unauthorized — `{"error":"…"}` |
+| 403 | Not authorized — `{"error":"…"}` |
+| 404 | Entity or company not found — `{"error":"…"}` |
+
+---
+
+_Generated from `@openapi` JSDoc. Do not edit by hand — run `npm run docs:api`._