Fix pagination in `/search` endpoint

Related to https://forum.db.nomics.world/t/search-pagination-in-next-api/162/3

How to reproduce:

• https://api.next.nomics.world/search?q=BOE&limit=20&offset=0
• https://api.next.nomics.world/search?q=BOE&limit=10&offset=0
• https://api.next.nomics.world/search?q=BOE&limit=10&offset=10

Problem: the 2 last URLs return the same result.

Expected: the 2nd URL should return the results 0-9 of the 1st URL, and the 3rd URL should return the next results 10-19.