Review and harden ZMQ DB backups: centralize backup decision, kill mutation survivor

By architect.

docs/reviews/zmq-db-backups-summary.md

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+# zmq-db-backups — Architect Review Summary
+
+**By architect.**
+
+## Task and commits reviewed
+- Task: `zmq-db-backups` (refactorer handoff, `merge_and_process refactorer 89731964de`)
+- Merged `swarmforge-refactorer` (fast-forward) — commits:
+  - `edcb8c8` Spec ZMQ-mode DB backups every epoch
+  - `2d193c6` Implement ZMQ-mode DB backups every epoch blocks (coder)
+  - `8973196` Refactor ZMQ DB backups: add property coverage and constructor test (refactorer)
+
+## Architectural findings and fixes
+- **Cohesion / DRY (fixed):** In `psf-memo-block-indexer.js` the IBD catch-up path
+  duplicated the backup decision (`if (nextBlockHeight % epoch === 0)`) that the
+  `BackupDb.maybeBackupDb` use case already encapsulates, while the ZMQ live path
+  correctly delegated the decision. Removed the redundant guard and now use the
+  use case's boolean return to decide whether to log. The decision now lives in
+  exactly one place.
+- **Boundaries (confirmed good):** `BackupDb` (use case) is a pure decision
+  function depending only on the `dbCtrl.backupDb` adapter interface; the HTTP
+  IO lives in `src/adapters/backup-db.js`. The use case is fully testable without
+  IO. No framework/persistence structures leak across the boundary.
+- **Hardening (added):** Added a unit test for the `height === 1` boundary to kill
+  a surviving mutation (`height > 0` → `height > 1`).
+
+## Verification results
+- **Language mutation** (`mutate4javascript`, `--max-workers 8`): `src/use-cases/backup-db.js`
+  — **6 killed, 0 survived, 0 uncovered** (after adding the `height === 1` test).
+- **CRAP** (`crap4javascript`): `BackupDb.maybeBackupDb` CC=3, 100% cov, CRAP=3.0
+  (threshold 8.0). Pass.
+- **DRY** (`dry4javascript`): no new duplication from this task. Pre-existing
+  duplicates in `rpc.js` and `set-name/set-profile/set-profile-pic` are out of
+  scope for this handoff.
+- **Soft Gherkin acceptance mutation** (`gherkin-mutator --level soft`): 11 killed,
+  **4 survived — all documented equivalents**. The survivors (m8, m9, m14, m15)
+  mutate height/epoch values in the two "0 backup" example rows to other
+  non-multiple values; the observable result (0 backups) is unchanged, so the
+  scenarios cannot distinguish them. No action needed.
+
+## Suite status
+- `psf-memo-indexer` unit: **54 passing** (was 53; +1 new boundary test)
+- `psf-memo-indexer` property: **4 passing**
+- `psf-memo-indexer` acceptance: **3 generated files, all passing**
+- `psf-memo-indexer` lint (`standard`): clean
+
+## Handoffs sent
+- `git_handoff` to coder and refactorer (`priority: 00`) with the review commit
+  for follow-up review.