Fix golangci unused/gofmt on the gentle-backfill path. Plot matrix and
line-chart X axes on the selected [requested_start, requested_end)
window (empty slots while backfill lags), and let plain mouse-wheel zoom
narrow the visible interval so pulse blocks grow wider.
Default channel_monitor_mode to v1 (opt-in V2) so upgrades keep active
probes; existing explicit v2 rows are left alone via ON CONFLICT DO NOTHING
plus migration checksum compatibility for already-applied 195.
V2 first-enable backfill no longer compresses ticks to 5s or uses 24h
chunks. Each tick does recent overlap plus at most one historical chunk
with depth-based ceilings (2h/4h/6h), adaptive grow/shrink, and failure
backoff. Error request_id dedup is bounded by a 90-minute lookback so
ops_error_logs is not scanned for full history.
Also align hide_throughput parse default with privacy-preserving public
runtime (missing key → true).
IanShaw027