Stats: range buttons follow the retention settings

The Statistics page offers only the ranges kept (longest of the minute,
hour and day retentions), adds 1y and 2y when the daily data covers them,
caps the heatmap at the hourly retention and links to Explore within
retention.queries. Status and explore send retention_seconds. The query
log error names stats.retention.queries.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/stats.md

@@ -263,7 +263,11 @@ database, roughly in proportion to the number of views.
   lists for `retention.hour`, daily ones for `retention.day`. Older data is
   deleted every hour.
 - Charts use the finest resolution that covers the range: minutes up to 48
-  hours, hours up to 90 days, days beyond.
+  hours (and `retention.minute`), hours up to `retention.hour`, days beyond.
+- The Statistics page offers only the ranges the data is kept for: up to 90
+  days with the defaults, plus a year and 2 years when `retention.day` (or
+  `retention.hour`) is that long. The Explore page offers the ranges up to
+  `retention.queries`.
 - Top lists are exact within an hour (up to 200,000 distinct names or
   clients per hour, beyond which the rarest are dropped). Daily lists are
   built from the hourly top lists, so for very long tails they are