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/database/database.go

@@ -0,0 +1,40 @@
+package database
+
+import (
+	"log"
+	"rrbec_server/internal/models"
+
+	"github.com/glebarez/sqlite"
+	"gorm.io/gorm"
+)
+
+var DB *gorm.DB
+
+func InitDB(dataSourceName string) *gorm.DB {
+	var err error
+	DB, err = gorm.Open(sqlite.Open(dataSourceName), &gorm.Config{})
+	if err != nil {
+		log.Fatalf("failed to connect database: %v", err)
+	}
+
+	// Auto Migration
+	err = DB.AutoMigrate(
+		&models.Mesa{},
+		&models.Client{},
+		&models.Category{},
+		&models.Product{},
+		&models.ProductComponent{},
+		&models.Comanda{},
+		&models.ProductComanda{},
+		&models.Order{},
+		&models.TypePay{},
+		&models.Payment{},
+		&models.User{},
+		&models.SyncState{},
+	)
+	if err != nil {
+		log.Fatalf("failed to migrate database: %v", err)
+	}
+
+	return DB
+}