Add IPv4 range optimization for IP to AS lookups

- Add v4_ip_start and v4_ip_end columns to live_routes table
- Calculate IPv4 CIDR ranges as 32-bit integers for fast lookups
- Update PrefixHandler to populate IPv4 range fields
- Add GetASInfoForIP method with optimized IPv4 queries
- Add comprehensive tests for IP conversion functions

internal/routewatch/prefixhandler.go

@@ -249,6 +249,20 @@ func (h *PrefixHandler) processAnnouncement(_ *database.Prefix, update prefixUpd
 		LastUpdated: update.timestamp,
 	}
 
+	// For IPv4, calculate the IP range
+	if ipVersion == ipv4Version {
+		start, end, err := database.CalculateIPv4Range(update.prefix)
+		if err == nil {
+			liveRoute.V4IPStart = &start
+			liveRoute.V4IPEnd = &end
+		} else {
+			h.logger.Error("Failed to calculate IPv4 range",
+				"prefix", update.prefix,
+				"error", err,
+			)
+		}
+	}
+
 	if err := h.db.UpsertLiveRoute(liveRoute); err != nil {
 		h.logger.Error("Failed to upsert live route",
 			"prefix", update.prefix,