test: integration tests for creator list filtered by multiple categories

[boys-cyberhub]

What changed

• Created creator-feed-multi-filter.integration.test.ts with a fixture set of 4 creators spanning verified/unverified and two search categories (jazz, rock).
• 20 test cases covering: verified + search, verified + sort + order, verified + search + pagination, full fixture set, serialized item shape, and pagination metadata consistency.
• Added jest.setup.ts + wired setupFiles in jest.config.js so Jest can run controller tests without real env vars.
• Fixed missing res.set mock in makeRes() in creator-feed-empty-filters.integration.test.ts so existing tests don't silently swallow responses.
• Fixed a pre-existing objectContaining({ verified: undefined }) assertion bug in the same file.

Why

Existing tests only covered empty-result filter paths. This adds fixture-backed tests that exercise the full filter combinator path — verified, search, sort, order, limit, offset — simultaneously, asserting that the correct params reach fetchCreatorList and the response envelope reflects real fixture data.

How to test

pnpm exec jest --testPathPatterns "creator-feed-multi-filter"
# → Tests: 20 passed
pnpm exec jest --testPathPatterns "creator-feed-empty-filters"
# → Tests: 26 passed (existing suite unbroken)

Closes #282