perf(xray): compile log/traffic regexps once at package scope (#5362)

GetTraffic recompiled two stats regexps on every traffic tick, and LogWriter.Write
recompiled two more on every log line. Hoist all four to package-level vars so they
compile once at load instead of per call on hot paths.

Co-authored-by: Sanaei <ho3ein.sanaei@gmail.com>

internal/xray/api.go

@@ -38,6 +38,13 @@ import (
 	"google.golang.org/grpc/status"
 )
 
+// Compiled once at package load: GetTraffic runs on every traffic-stats tick,
+// so recompiling these per call is wasted work.
+var (
+	trafficRegex       = regexp.MustCompile(`(inbound|outbound)>>>([^>]+)>>>traffic>>>(downlink|uplink)`)
+	clientTrafficRegex = regexp.MustCompile(`user>>>([^>]+)>>>traffic>>>(downlink|uplink)`)
+)
+
 // XrayAPI is a gRPC client for managing Xray core configuration, inbounds, outbounds, and statistics.
 type XrayAPI struct {
 	HandlerServiceClient *command.HandlerServiceClient
@@ -537,9 +544,6 @@ func (x *XrayAPI) GetTraffic() ([]*Traffic, []*ClientTraffic, error) {
 		return nil, nil, common.NewError("xray api is not initialized")
 	}
 
-	trafficRegex := regexp.MustCompile(`(inbound|outbound)>>>([^>]+)>>>traffic>>>(downlink|uplink)`)
-	clientTrafficRegex := regexp.MustCompile(`user>>>([^>]+)>>>traffic>>>(downlink|uplink)`)
-
 	ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
 	defer cancel()