Add IP information API with background WHOIS fetcher

- Add /ip and /ip/{addr} JSON endpoints returning comprehensive IP info
- Include ASN, netblock, country code, org name, abuse contact, RIR data
- Extend ASN schema with WHOIS fields (country, org, abuse contact, etc)
- Create background WHOIS fetcher for rate-limited ASN info updates
- Store raw WHOIS responses for debugging and data preservation
- Queue on-demand WHOIS lookups when stale data is requested
- Refactor handleIPInfo to serve all IP endpoints consistently

internal/server/routes.go

@@ -30,7 +30,13 @@ func (s *Server) setupRoutes() {
 	r.Get("/prefix/{prefix}", s.handlePrefixDetail())
 	r.Get("/prefixlength/{length}", s.handlePrefixLength())
 	r.Get("/prefixlength6/{length}", s.handlePrefixLength6())
-	r.Get("/ip/{ip}", s.handleIPRedirect())
+
+	// IP info JSON endpoints (replaces old /ip redirect)
+	r.Route("/ip", func(r chi.Router) {
+		r.Use(JSONValidationMiddleware)
+		r.Get("/", s.handleIPInfo())       // Client IP
+		r.Get("/{addr}", s.handleIPInfo()) // Specified IP
+	})
 
 	// API routes
 	r.Route("/api/v1", func(r chi.Router) {