Add customergroup bulk reorder and list editable flag.

Expose PUT /customergroup/order for exact-set sort updates, keep create/update name-only, and mark POS/Lieferanten as non-editable in list responses.

src/api/openapi.js

@@ -126,12 +126,26 @@
  *           format: date-time
  *     Customergroup:
  *       type: object
- *       required: [id, name]
+ *       required: [id, name, sort]
  *       properties:
  *         id:
  *           type: integer
  *         name:
  *           type: string
+ *         sort:
+ *           type: integer
+ *     CustomergroupListItem:
+ *       allOf:
+ *         - $ref: '#/components/schemas/Customergroup'
+ *         - type: object
+ *           required: [editable]
+ *           properties:
+ *             editable:
+ *               type: boolean
+ *               description: |
+ *                 `false` for implicit groups `POS` and `Lieferanten` (name locked).
+ *                 `true` for user-created groups. Reorder all groups via
+ *                 `PUT /customergroup/order`.
  *     Entity:
  *       type: object
  *       required: [id, customergroupId, firstName, name, createdAt, updatedAt]