Add pagination metadata to API responses

[masahirodev]

Description

Currently, the API returns only the items array without any pagination metadata.
Clients cannot determine if more data is available.

Expected Format

{
  "items": [
    { "id": 1, "name": "Apple" },
    { "id": 2, "name": "Banana" }
  ],
  "nextPageToken": "abc123",
  "hasNextPage": true
}