Docker container URL preserved on update (#1054): container updates
recreate the container with a new runtime ID. The agent now includes
{oldContainerId, newContainerId} in the completion ACK payload; the
server uses this to copy persisted metadata (custom URLs, descriptions,
tags) to the new ID so nothing is lost. Migration is a copy, not a move,
so rollback scenarios still find metadata under the original ID.
Reduce metrics.db write amplification (#1124): add a UNIQUE index on
(resource_type, resource_id, metric_type, timestamp, tier) so rollup
reprocessing after a failed checkpoint uses INSERT OR IGNORE instead of
creating duplicate rows. Existing duplicates are deduplicated once on
startup if the index creation would otherwise fail. Also sets
wal_autocheckpoint(500) to checkpoint the WAL more frequently, preventing
unbounded WAL growth.
Fixes#1054Fixes#1124
