test(bulletin): add unit test for getPageItems pagination

[andrecamerino]

Description

Adds this repo's first real unit test, proving the Vitest/RTL setup from #347 actually works end to end. This is PR 3 of a 4-part stack (base: ci/wire-up-test-workflow):

1. chore(testing): set up vitest and react testing library #347 - Vitest + RTL tooling
2. chore(ci): wire pnpm test into CI and split into parallel jobs #352 - CI wiring
3. This PR - unit test example
4. Integration test example (Payload + Mongo round-trip)

Target: getPageItems (src/components/bulletin/AllArticles.tsx) - the pagination-window algorithm that turns (totalPages, currentPage) into the list of page numbers/ellipses the pager renders. It's a plain function (no rendering, no DB), so this is a pure "unit test" - deterministic and isolated, deliberately picked over a trivial formatter since it has real branching logic worth locking down (short vs. long page lists, ellipsis placement on either/both sides).

Changes:

• Added export to getPageItems and the ELLIPSIS const it returns - previously module-private, no behavior change.
• New src/components/bulletin/AllArticles.test.tsx, colocated with the component it covers, with a comment noting that convention (test file next to source, *.test.ts(x)) for future contributors. Covers: all-pages-shown for small totals, single-page, windowing with ellipsis on both/one/neither side.

Part of #182 (satisfies the "sample test file exists" AC item)

Note

Because #352 (CI wiring) now sits below this PR in the stack, this PR's own CI run actually exercises the test job against these tests - not just local pnpm test output.

Decisions

• Colocated rather than placed under tests/ - this test is tied to one specific file, so it lives next to it. tests/ is reserved for cross-cutting concerns (setup helpers, things that don't belong to a single source file).

AI Usage

• AI was used to generate this PR
• I personally reviewed and understood the code if generated by AI (you should be able to explain every changed line in review)

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• Manual testing — screenshots or a short video must be attached below for any UI change
• npm run lint and npm run build pass locally

pnpm test (5/5 passing), pnpm lint, and pnpm format:check were run locally and pass clean. pnpm build was not run locally in this session (no local DB/env configured) - CI's Build job will verify it.

[evanautianle]

yurrrrpppp looks good great work andre