fix(rereview): close export-flip race + queue-dedup reload regression

Adversarial re-review of the persona-audit + audit-followup rounds (6411747..)
found one HIGH and one MED regression plus LOW gaps. All fixed with coverage.

HIGH — export stale-keepsake resurrected by an open_event race
  A reopen landing in the window between a *current* export worker's finalize_job
  and its ready-flag flip cleared export_released_at + the ready flags but left the
  export_job row `done` at the same release_seq. The seq-guarded flip then still
  matched and re-set export_{zip,html}_ready=TRUE on a pre-reopen snapshot; the next
  re-release read that stale TRUE and skipped regeneration (`if ready { continue }`),
  serving a keepsake missing every upload from the reopen window — the exact data
  loss migration 012 exists to prevent. Both ready-flip UPDATEs are now additionally
  anchored on `export_released_at IS NOT NULL`, so a landed reopen makes the flip a
  no-op and the re-release regenerates cleanly.

MED — queue dedup broke for reloaded items
  loadQueue rebuilt QueueItems from IndexedDB without copying lastModified, which the
  new addToQueue dedup keys on. A file re-selected after a page reload / PWA relaunch
  missed the duplicate check and uploaded twice. Rehydration now carries lastModified
  (extracted to a pure, tested entryToQueueItem helper).

LOW
  - diashow: clear the upload-processed debounce timer in onDestroy (no stray
    post-unmount /feed fetch).
  - USER_JOURNEYS §9.5: document the reconnect-delta ban replay (hidden_user_ids /
    uploads_hidden_at, migration 013), not just the live user-hidden SSE.
  - e2e api-client: drop the misleading hide_uploads param from banUser — the backend
    takes no body and always hides; strip the dead boolean at all call sites.

Tests
  - Extract isReversibleLock (the terminal-403 KEEP-vs-PURGE-blob discriminator) into a
    pure exported helper + unit tests, so the data-loss-critical branch is covered
    without an XHR harness.
  - entryToQueueItem unit tests lock the lastModified-carry regression.
  - Document the export flip-race guard in the reopen/re-release spec (the sub-ms
    finalize↔flip interleave isn't deterministically forceable with fast fixtures;
    covered by the SQL guard + the end-to-end completeness test).

Verified: backend 40 tests, frontend 44 unit tests, svelte-check 0 errors,
e2e 156 passed / 1 skipped on chromium-desktop.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

e2e/specs/10-flow-review/export-reopen-rerelease.spec.ts

@@ -17,6 +17,18 @@
  * superseded worker discards its output instead of resurrecting a stale keepsake. The
  * download follows the current `done` row's `file_path`, never a fixed name.
  *
+ * A second, narrower window on the SAME class of bug (fixed alongside): a reopen (`open_event`)
+ * landing between a *current* worker's `finalize_job` and its ready-flag flip. `open_event`
+ * clears `export_released_at` + both ready flags but leaves the `export_job` row `done` at the
+ * current seq — so the seq-guarded flip would still match and resurrect `export_zip_ready=TRUE`
+ * on a pre-reopen snapshot, and the next re-release would `if ready { continue }` and skip
+ * regeneration. The flip UPDATEs are therefore additionally anchored on
+ * `export_released_at IS NOT NULL`, making them a no-op once a reopen has landed. The
+ * "completeness" test below exercises the real reopen→re-release worker path end-to-end; the
+ * sub-millisecond finalize↔flip interleave itself isn't deterministically forceable with the
+ * fast fixtures, so that exact window is covered by the SQL guard + code review rather than a
+ * timing-dependent assertion.
+ *
  * Coverage:
  *  - churn integrity: rapid reopen→re-release yields exactly one INTACT ZIP, no stuck jobs.
  *  - completeness: an upload added during the reopen window IS present in the re-released