Admin Run Annotation Queue

Manually trigger the brief-review annotation-queue router.

Same code path as python -m app.cron.annotation_queue. Read-mostly scan of recent brief_pipeline traces that routes errored / low-rated / venue-out-of- band / internal-terms briefs into the LangSmith annotation queue. Returns the run summary (candidates, per-signal counts, added) so you can smoke-test the selection without waiting for the cron tick.

DRY-RUN BY DEFAULT — set ANNOTATION_QUEUE_DRY_RUN=false to actually populate the queue once a dry-run's selection looks right.