fix(publish): prevent stuck publish queue and duplicate posting

The desktop publish queue could stall for a long time and end users assumed
the software was broken. Root cause: a hung adapter held its execution slot
with no wall-clock timeout while auto-renewing its lease forever, so the
server never reclaimed it and every queued task behind it stayed 等待发布.
Auto-recovery also risked silently re-posting a non-idempotent article.

Client (Electron):
- per-task wall-clock deadline + abort; progress-gated lease renewal that
  stops and aborts a stalled task instead of renewing it forever
- decouple the concurrency cap from CDP-induced CPU/memory pressure
  (admission gate instead of self-throttling collapse); 15s watchdog pump
- all adapter network I/O now has fetch timeouts and honors context.signal;
  bounded image-upload concurrency with per-image timeout
- surface live adapter progress, elapsed time, queue position and a
  working-vs-queued distinction in the publish view

Server (tenant-api):
- publish lease-recovery worker (every 3m) + supporting index: reclaim
  expired in_progress publish leases, requeue (<3 attempts) or terminal-fail
- 3-minute lease TTL with client-presence-gated extension; max 3 attempts

Idempotency (production-grade core):
- durable publish_submit_started_at marker, set before the irreversible
  platform submit POST; recovery and abort route a maybe-submitted task to
  unknown (manual reconcile, kept in the dedup set) instead of re-posting
- desktop UI requires explicit confirmation before retrying a possibly-
  already-published task

Verified: go build/vet/test (incl. resolvePublishRecoveryOutcome), vue-tsc,
vitest 141/141, gofmt all clean.

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

server/internal/tenant/transport/router.go

@@ -66,6 +66,7 @@ func RegisterRoutes(app *bootstrap.App) {
 	desktopAuth.POST("/tasks/lease", desktopTaskHandler.Lease)
 	desktopAuth.POST("/tasks/:id/lease", desktopTaskHandler.Lease)
 	desktopAuth.POST("/tasks/:id/extend", desktopTaskHandler.Extend)
+	desktopAuth.POST("/tasks/:id/publish-submit-marker", desktopTaskHandler.MarkPublishSubmitStarted)
 	desktopAuth.POST("/tasks/:id/cancel", desktopTaskHandler.Cancel)
 	desktopAuth.POST("/tasks/:id/result", desktopTaskHandler.Result)
 	desktopAuth.POST("/publish-tasks/:id/retry", desktopTaskHandler.RetryPublish)