refactor: extract pkg/forward and pkg/luaplugin packages

Move ForwardManager → pkg/forward/Manager and PluginManager →
pkg/luaplugin/Manager. Move FoeWardMode (now forward.Mode) with
ParseMode/Network/String into pkg/forward. Rename constants:
NOT→None, TCPC→TCP, UDPC→UDP. Update all references in main
package.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

config.go

@@ -3,7 +3,6 @@ package main
 import (
 	"fmt"
 	"os"
-	"strings"
 	"time"
 )
 
@@ -27,49 +26,8 @@ type Config struct {
 	hotkeyMod   string
 }
 
-type FoeWardMode int
-
-const (
-	NOT FoeWardMode = iota
-	TCPC
-	UDPC
-)
-
 var config Config
 
-func (m FoeWardMode) Network() string {
-	switch m {
-	case TCPC:
-		return "tcp"
-	case UDPC:
-		return "udp"
-	default:
-		return ""
-	}
-}
-
-func (m FoeWardMode) String() string {
-	switch m {
-	case TCPC:
-		return "tcp"
-	case UDPC:
-		return "udp"
-	default:
-		return "none"
-	}
-}
-
-func parseForwardMode(v string) (FoeWardMode, bool) {
-	switch strings.ToLower(strings.TrimSpace(v)) {
-	case "tcp", "tcp-c", "tcpc", "1":
-		return TCPC, true
-	case "udp", "udp-c", "udpc", "2":
-		return UDPC, true
-	default:
-		return NOT, false
-	}
-}
-
 func openLogFile() (*os.File, error) {
 	if config.enableLog {
 		path := fmt.Sprintf(config.logFilePath, config.portName, time.Now().Format("2006_01_02T150405"))