get_recent_packets/1 and get_recent_packets_for_map/1 now accept a
:cursor option (%{received_at: DateTime, id: uuid}) instead of :offset
for deep paging. On the 100M-row partitioned packets table, offset
scanning was linear in page depth; keyset is constant.
Ordering tightened to (received_at DESC, id DESC) so the cursor is
stable across ties. idx_packets_received_desc still covers the lookup;
a dedicated (received_at DESC, id DESC) index isn't worth its size
given microsecond timestamp granularity.
historical_loader migrated from batch_offset*batch_size scheduling to
a sequential cursor chain. The old loader fanned out N Process.send_after
batches up-front which could arrive out-of-order; the cursor version
waits for batch N before scheduling N+1, and also short-circuits the
remaining schedule when an under-full batch signals exhaustion.
mobile_channel load_historical_packets dropped its meaningless
`offset: 0`; callsign history already lacked offset.
No LiveView or WebSocket payload shapes changed. offset: 0 (or omitted)
still behaves as first page; non-zero offsets are silently ignored.
Graham McIntire
f225f57044