Add route age information to IP lookup API

- Add last_updated timestamp and age fields to ASInfo
- Include route's last_updated time from live_routes table
- Calculate and display age as human-readable duration
- Update both IPv4 and IPv6 queries to fetch timestamp
- Fix error handling to return 400 for invalid IPs

internal/server/server.go

@@ -4,6 +4,7 @@ package server
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"net/http"
 	"os"
 	"runtime"
@@ -439,7 +440,13 @@ func (s *Server) handleIPLookup() http.HandlerFunc {
 		// Look up AS information for the IP
 		asInfo, err := s.db.GetASInfoForIP(ip)
 		if err != nil {
-			writeJSONError(w, http.StatusNotFound, err.Error())
+			// Check if it's an invalid IP error
+			if errors.Is(err, database.ErrInvalidIP) {
+				writeJSONError(w, http.StatusBadRequest, err.Error())
+			} else {
+				// All other errors (including ErrNoRoute) are 404
+				writeJSONError(w, http.StatusNotFound, err.Error())
+			}
 
 			return
 		}