Add oldest and newest route timestamps to status page

Display oldest and newest route timestamps in the Routing Table card
on the /status page. Timestamps are shown as relative times (e.g.,
"5m ago", "2h 30m ago").

Changes:
- Add OldestRoute and NewestRoute fields to database.Stats
- Query MIN/MAX of last_updated across live_routes_v4 and v6 tables
- Include timestamps in both /status.json and /api/v1/stats responses
- Add formatRelativeTime JavaScript function for display

internal/database/database.go

@@ -946,6 +946,23 @@ func (d *Database) GetStatsContext(ctx context.Context) (Stats, error) {
 	}
 	stats.LiveRoutes = v4Count + v6Count
 
+	// Get oldest and newest route timestamps
+	routeTimestampQuery := `
+		SELECT MIN(last_updated), MAX(last_updated) FROM (
+			SELECT last_updated FROM live_routes_v4
+			UNION ALL
+			SELECT last_updated FROM live_routes_v6
+		)
+	`
+	var oldestRoute, newestRoute *time.Time
+	err = d.db.QueryRowContext(ctx, routeTimestampQuery).Scan(&oldestRoute, &newestRoute)
+	if err != nil {
+		d.logger.Warn("Failed to get route timestamps", "error", err)
+	} else {
+		stats.OldestRoute = oldestRoute
+		stats.NewestRoute = newestRoute
+	}
+
 	// Get prefix distribution
 	stats.IPv4PrefixDistribution, stats.IPv6PrefixDistribution, err = d.GetPrefixDistributionContext(ctx)
 	if err != nil {

internal/database/interface.go

@@ -18,6 +18,8 @@ type Stats struct {
 	Peers                  int
 	FileSizeBytes          int64
 	LiveRoutes             int
+	OldestRoute            *time.Time
+	NewestRoute            *time.Time
 	IPv4PrefixDistribution []PrefixDistribution
 	IPv6PrefixDistribution []PrefixDistribution
 }