fix(ci): allowlist /content/topics* in srv-qa route-drift guard

[jung-thomas]

Problem

The unit CI job fails at the Static build guards (postbuild:apps) step:

[check-srv-qa-route-drift] FAILED — /content/* route drift detected:
  Routes on srv but MISSING from srv-qa/server.js:
    GET /content/topics/:slug    (srv/server.js:551)
    GET /content/topics-index    (srv/server.js:590)
    POST /content/publish/render-topics    (srv/server.js:633)

The tag-tree-topics feature (#2099) added three /content/topics* routes to srv/server.js. The route-drift guard requires every /content/* route to be mirrored in srv-qa/server.js or explicitly allowlisted.

Fix

Topic landing pages are a public prod content surface — they mirror /content/concepts* (topic-prefixed BLOBs, legacy-slug 301 resolution, publish-session rendering) — not tutorial-draft author preview. The QA channel serves in-flight tutorials from -Contribution repos; topic pages are out of its scope and srv-qa wires no topic serve/publish flow.

So the correct fix is to add the three routes to ALLOWLIST_ONLY_ON_SRV with justifications (same treatment as concepts/authors/advocates/puzzles), rather than pulling publish-topics.js/topic-list-page.js deps into the srv-qa cp list for an unreachable surface.

Verification

npm run postbuild:apps passes end-to-end locally:

[check-srv-qa-route-drift] OK — 33 /content/* route(s) on srv, 13 on srv-qa (20 srv-only + 0 srv-qa-only allowlisted).
...
ok — 0 deprecated-only changes, 0 unmitigated