bug: Admin applications-by-status endpoint returns 500 when the result set is empty

[nora-weisser]

GET /api/platform/v1/admin/mentorship/cycles/{cycleId}/applications?status=... returns 500 Internal Server Error whenever the cycle has no applications matching the requested statuses. The endpoint cannot legitimately return an empty list — every admin portal tab that queries an empty bucket (common on a fresh cycle or QA environment) fails instead of showing "no results".

Steps to reproduce

1. In the admin portal, open the applications view for a cycle that has no applications in PENDING or MENTOR_REVIEWING.
2. Observe the failed network call to GET /admin/mentorship/cycles/{cycleId}/applications?status=PENDING,MENTOR_REVIEWING.
3. Or call directly with X-API-KEY and a bearer token on any cycle / status combination that matches no records.

Expected

• 200 OK with an empty array [].

Actual

• 500 Internal Server Error. Server logs show BadSqlGrammarException with the underlying message syntax error at or near ")" from a generated query of the shape SELECT * FROM mentees WHERE mentee_id IN ().