Show figures of the routing table on the home page (closes #154)

The home page gets cards for the newest and oldest kept route, the newest
and oldest updated AS, the AS with the most prefixes, the ASes with a
single prefix and fifteen well-known networks. Two more cards count the
bogon announcements and the prefixes with several origin ASes. They link
to the new pages /bogons and /multiple-origins, which list up to 1,000
entries each.

The new package internal/bogon tells reserved prefixes and AS numbers,
from the IANA special-purpose and address space registries. Table.Overview
walks the table and lets the read lock go every 10,000 prefixes. The
server works the cards out once a minute and serves that copy. A new index
on asns(last_seen) finds the newest and oldest updated AS.

Model: opus-5-5

internal/templates/templates_test.go

@@ -12,13 +12,17 @@ import (
 )
 
 // renderPage renders a page with the data every page needs, and the visitor's
-// address, which the home page also needs.
+// address and the routing table's cards, which the home page also needs. The
+// cards are left out, as before the server first works them out.
 func renderPage(t *testing.T, tmpl *template.Template) string {
 	t.Helper()
 
 	var page bytes.Buffer
 
-	err := tmpl.Execute(&page, struct{ CSPNonce, ClientIP string }{})
+	err := tmpl.Execute(&page, struct {
+		CSPNonce, ClientIP string
+		Cards              any
+	}{})
 	if err != nil {
 		t.Fatalf("rendering the page: %v", err)
 	}