status/backlog(2): Q4.6 discourse blocked (bitnami images gone); pivot to Q4.9 mailu (images pullable)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

machine-docs/BACKLOG-2.md

@@ -177,7 +177,13 @@ Phase plan: `/srv/cc-ci/cc-ci-plan/plan-phase2-recipe-tests.md`
       backup data-integrity (seed→backup→mutate→restore→assert) = follow-up ops.py — tracked in the Q5
       P4-sweep (generic backup/restore covers the floor; same bar as ghost Q4.4). Mirror to
       recipe-maintainers needed only for the PR/!testme flow (catalogue-fetch e2e green now).
-- [ ] **Q4.6** — discourse: enroll; specific (create-a-topic round-trip).
+- [~] **Q4.6** — discourse: **BLOCKED (DEFERRED 2026-05-29)** — upstream recipe pins
+      `bitnami/discourse:*` images that Docker Hub no longer serves (manifest unknown; swarm task
+      Rejected 'No such image'). db/redis deploy; bitnami-imaged app/sidekiq cannot. Image exists at
+      `bitnamilegacy/discourse` but the install tier uses the prev published version (also gone), so a
+      recipe-PR can't unblock testing until upstream releases a fixed version. Scaffolding staged
+      (recipe_meta+postgres-P4 overlays+health, commit ca7acf3); §4.3 create-topic not written (deploy
+      blocked). See DEFERRED.md 2026-05-29 discourse entry. Same class as plausible Q4.7b.
 - [~] **Q4.7** — plausible: enrolled. recipe_meta (DISABLE_AUTH/REGISTRATION, SECRET_KEY_BASE;
       HEALTH_PATH=/api/health [200 w/ clickhouse+postgres+sites_cache ok — `/` 500s under headless
       DISABLE_AUTH so not a valid probe]; DEPLOY/HTTP_TIMEOUT=1200) + PARITY.md (P2 vacuous, no