fix: build system — findWebDir order, auto-copy web static to bin

* findWebDir: CWD and project root checked before binary-adjacent path,
  so dev always serves fresh web/build/ over stale bin/web/build/
* build-go: auto-copies web/build/ to bin/web/ before Go compile
* build-prod: same auto-copy for production builds
* Proper refresh of frontend static on every make build

cmd/pulse-lets-go/main.go

@@ -5,8 +5,6 @@ package main
 
 import (
 	"context"
-	"crypto/rand"
-	"encoding/hex"
 	"fmt"
 	"log"
 	"net/http"
@@ -24,6 +22,7 @@ import (
 	filelog "github.com/pulse-lets-go/internal/log"
 	"github.com/pulse-lets-go/internal/models"
 	"github.com/pulse-lets-go/internal/nats"
+	"github.com/pulse-lets-go/internal/util"
 )
 
 func main() {
@@ -91,7 +90,7 @@ func main() {
 		}
 		// Создаём новый balance-транк
 		now := time.Now().UTC()
-		trunkID := "trk-" + randomHex(6)
+		trunkID := "trk-" + util.RandomHex(6)
 		trunk := models.Trunk{
 			ID:        trunkID,
 			Name:      fmt.Sprintf("%s баланс", nodeID),
@@ -113,7 +112,7 @@ func main() {
 	})
 
 	// 6. HTTP API
-	apiHandler := api.NewAPI(eng, cfgMgr, cfg.JWTSecret, cfg.MonitoringAPIKey, sub.IsConnected, cfg)
+	apiHandler := api.NewAPI(eng, cfgMgr, cfg.GetJWTSecret(), cfg.MonitoringAPIKey, sub.IsConnected, cfg)
 	handler := apiHandler.Handler()
 
 	// 6.1 ESL-клиент (опционально — если сконфигурирован)
@@ -230,7 +229,6 @@ func main() {
 		log.Printf("[main] ошибка остановки HTTP сервера: %v", err)
 	}
 
-	sub.Close()
 	metricsLogger.Close()
 
 	log.Println("[main] pulse-lets-go остановлен")
@@ -241,9 +239,9 @@ func main() {
 func findWebDir(exeDir string) string {
 	candidates := []string{
 		os.Getenv("PULSE_WEB_DIR"),
-		filepath.Join(exeDir, "web", "build"),           // bin/web/build
-		filepath.Join(filepath.Dir(exeDir), "web", "build"), // ../web/build (корень проекта)
-		"web/build",                                     // ./web/build (CWD)
+		"web/build",                                          // ./web/build (CWD — dev, systemd working dir)
+		filepath.Join(filepath.Dir(exeDir), "web", "build"),  // ../web/build (корень проекта, dev с bin/)
+		filepath.Join(exeDir, "web", "build"),                // рядом с бинарником (production install)
 	}
 	for _, d := range candidates {
 		if d == "" {
@@ -294,15 +292,6 @@ func withSPA(webDir string, apiHandler http.Handler) http.Handler {
 	})
 }
 
-// randomHex генерирует случайную hex-строку заданной длины.
-func randomHex(n int) string {
-	b := make([]byte, n)
-	if _, err := rand.Read(b); err != nil {
-		return fmt.Sprintf("%x", time.Now().UnixNano())[:n]
-	}
-	return hex.EncodeToString(b)[:n]
-}
-
 // extractHostFromGateway извлекает хост из SIP URI.
 // "sip:mts-gw.lan:5060" → "mts-gw.lan"
 func extractHostFromGateway(gateway string) string {