Add /ip/<ip> route that redirects to prefix detail page

- Implement handleIPRedirect handler that looks up the prefix containing an IP
- Add /ip/{ip} route to routes.go
- Reuse existing GetASInfoForIP database method which returns prefix info
- Redirect to /prefix/<prefix> page with HTTP 303 See Other status
- Handle invalid IPs (400) and IPs with no route (404)

internal/server/routes.go

@@ -28,6 +28,7 @@ func (s *Server) setupRoutes() {
 	// AS and prefix detail pages
 	r.Get("/as/{asn}", s.handleASDetail())
 	r.Get("/prefix/{prefix}", s.handlePrefixDetail())
+	r.Get("/ip/{ip}", s.handleIPRedirect())
 
 	// API routes
 	r.Route("/api/v1", func(r chi.Router) {