warm_grid_cache_and_broadcast was re-SELECTing 92k hrrr_profiles rows
with JSONB profile/duct_characteristics columns on every forecast hour.
Row decoding exceeded the 15s default DB connection timeout, killing
the worker before f01-f18 could run. Oban retried from f00 and got
stuck in a loop: for the last several hours, no forecast hours were
being written and even f00 was stale.
Build the weather cache rows directly from the in-memory grid_data
the worker already has (Weather.build_grid_cache_rows/2) and
GridCache.broadcast_put directly. No DB round trip, no JSONB decode.
Also widen the cron from hourly to every 3 hours so a full f00-f18
sweep (~95 min) can actually complete before the next run starts,
and drop the redundant prune_old_scores() at worker start
(PropagationPruneWorker already runs every 15 min). Add a 60s query
timeout to load_weather_grid_from_db as defense-in-depth for the
cold-cache fill path that still uses it.