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>

internal/stats/collector.go

@@ -95,6 +95,13 @@ type Status struct {
 		Day     string `json:"day"`
 		Queries string `json:"queries"` // the query log ("" when off)
 	} `json:"retention"`
+	// RetentionSeconds is Retention in seconds, for the web UI's ranges.
+	RetentionSeconds struct {
+		Minute  int64 `json:"minute"`
+		Hour    int64 `json:"hour"`
+		Day     int64 `json:"day"`
+		Queries int64 `json:"queries"` // 0 when the query log is off
+	} `json:"retention_seconds"`
 }
 
 // Collector gathers statistics into a Store.
@@ -164,8 +171,12 @@ func NewCollector(store *Store, opts Options, zones ZoneIndex, log *slog.Logger)
 	c.status.Retention.Minute = humanDuration(opts.RetainMinute)
 	c.status.Retention.Hour = humanDuration(opts.RetainHour)
 	c.status.Retention.Day = humanDuration(opts.RetainDay)
+	c.status.RetentionSeconds.Minute = int64(opts.RetainMinute / time.Second)
+	c.status.RetentionSeconds.Hour = int64(opts.RetainHour / time.Second)
+	c.status.RetentionSeconds.Day = int64(opts.RetainDay / time.Second)
 	if opts.QueryLog && opts.RetainQueries > 0 {
 		c.status.Retention.Queries = humanDuration(opts.RetainQueries)
+		c.status.RetentionSeconds.Queries = int64(opts.RetainQueries / time.Second)
 	}
 	return c
 }