feat: null-safe creator list envelope and multi-filter integration tests

[boys-cyberhub]

What changed

• Add response envelope consistency check for empty list vs null list #281 — Null-safe response envelope for creator list:

  • Added normalizeCreatorListItems() helper in creators.serializers.ts that coerces null | undefined to [] before mapping.
  • Updated serializeCreatorList() to accept CreatorProfile[] | null | undefined and call the normalizer.
  • Updated wrapPublicCreatorListResponse() in public-creator-list-envelope.utils.ts to coerce null | undefined items to [] at the envelope level (defence-in-depth).
  • Extended creator-feed-empty-filters.integration.test.ts with 3 tests asserting that items is always an array when the data layer returns null or undefined.

• Add integration test for creator list filtered by multiple categories simultaneously #282 — Integration tests for multiple category filters with fixture data:

  • Created creator-feed-multi-filter.integration.test.ts with a fixture set of 4 creators spanning verified/unverified and two search categories.
  • 20 test cases covering verified + search, verified + sort + order, verified + search + pagination, full-fixture set, item shape validation, and paginations metadata consistency.
  • Asserts that fetchCreatorList receives the correct combination of filter params and that the response envelope serializes non-empty fixture data correctly.

• Test infrastructure: Added jest.setup.ts with stub environment variable values and wired it into jest.config.js via setupFiles, enabling Jest to run modules that transitively import src/config.ts.

  • Also fixed a pre-existing assertion bug in creator-feed-empty-filters.integration.test.ts where objectContaining({ verified: undefined }) incorrectly assumed Zod emits optional keys with undefined values (it omits them).

Why

Empty-array guarantee prevents client-side items.forEach / items.map from throwing when an unexpected null propagates from the data layer. The multi-filter integration tests exercise the filter combinator path end-to-end with real fixture data rather than empty mocks.

How to test

pnpm exec jest --testPathPatterns "creator-feed-empty-filters" "creator-feed-multi-filter"
# → Test Suites: 2 passed | Tests: 44 passed

Closes #281
Closes #282

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[boys-cyberhub]

Splitting into separate PRs per issue as requested by maintainer.