feat: RRBEC Local Server - Go backend with Django sync

- Implement local-first architecture with SQLite
- Add bidirectional sync with Django via ChangeLog
- JWT authentication with auto-refresh token
- REST API for products, orders, commands, payments
- Stock management with automatic deduction

rrbec_server/internal/config/config.go

@@ -0,0 +1,40 @@
+package config
+
+import (
+	"log"
+	"os"
+
+	"github.com/joho/godotenv"
+)
+
+type Config struct {
+	Port                string
+	DBName              string
+	DjangoBaseURL       string
+	DjangoMasterUser    string
+	DjangoMasterPassword string
+}
+
+var AppConfig *Config
+
+func LoadConfig() {
+	err := godotenv.Load()
+	if err != nil {
+		log.Println("No .env file found, using defaults")
+	}
+
+	AppConfig = &Config{
+		Port:                 getEnv("PORT", "8080"),
+		DBName:               getEnv("DB_NAME", "rrbec.db"),
+		DjangoBaseURL:        getEnv("DJANGO_BASE_URL", ""),
+		DjangoMasterUser:     getEnv("DJANGO_MASTER_USER", ""),
+		DjangoMasterPassword: getEnv("DJANGO_MASTER_PASSWORD", ""),
+	}
+}
+
+func getEnv(key, fallback string) string {
+	if value, ok := os.LookupEnv(key); ok {
+		return value
+	}
+	return fallback
+}