* feat(db): observer adverts on a partial index once observations carry their payload type
* fix(db): keep today's adverts statement unguarded and rate-limit the gate's read warning
* feat(background): batched, resumable payload-type backfill for untyped observations
* fix(background): cap each payload-type backfill statement at 50,000 rows
* fix(db): reject a non-positive backfill row cap
* perf(db): probe rollups per hour and IATA for region-sized stats lists
* fix(db): keep the stats probes inside each rollup table's hour range
* test(db): push the far-future until to year 9999 so a missing path-stats end bound times out
* perf(db): row-comparison trace cursor and a since-only telemetry statement
* test(db): pin the empty trace cursor tag and run the trace pagination tests in CI
* test(planguard): stats, adverts, traces and telemetry statements leave pending; diff cases
* test(planguard): window-bounded advert roles, short quiet page, per-observer telemetry cursors
Stats endpoints read hourly rollup tables filled once per closed hour by one
advisory-locked task, instead of materialized views that re-scanned every
observation on each refresh. IATA-set tables give exact distinct counts for any
IATA set or region. Cleanup holds raw rows for unrolled hours (up to 24h).
Adds /stats/series; ingest keeps packet observation counts, observer last IATA,
channel message counts and trace tag summaries. 001_baseline.sql is rewritten,
so pre-release 2.0 databases must be recreated. See docs/historical-stats.md.
MrAlders0n