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 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/server/routes.go

@@ -55,6 +55,10 @@ func (s *Server) setupRoutes() {
 	r.Get("/prefixlength/{length}", s.handlePrefixLength())
 	r.Get("/prefixlength6/{length}", s.handlePrefixLength6())
 
+	// The pages that list what two of the home page's cards count
+	r.Get("/bogons", s.handleBogons())
+	r.Get("/multiple-origins", s.handleMultipleOrigins())
+
 	// The JSON routes answer a path or method they do not take with the JSON
 	// error body, as they answer everything else.
 	jsonNotFound := func(w http.ResponseWriter, _ *http.Request) {