fix flaky test case

[dev-rminds]

Changes description

Case: https://github.com/teamforus/forus-backend/actions/runs/12279849695/attempts/1
Fixed by creating a new fund during the test instead of using the seed data.

Developers checklist

• Autotests are passed locally
• Migration rollback works - if there is migration, check rollback
• Autotests are added:
  • bugfix - unit/feature test for this scenario if possible
  • new small/medium feature - simple feature test for positive scenarios

QA checklist

• Translations are done
• Endpoint is fast on dump - if there is new endpoint or changed query, endpoints that are using changed query - working fast on production dump, <2s