chore: initial project scaffold with admin web, backend, desktop client, and deployment setup

Add monorepo structure for NexaVPN WireGuard control plane including:
- .gitignore for node_modules, build artifacts, and environment files
- README with project overview, monorepo layout, and quick start guide
- Admin web UI with React, Vite, TypeScript, and nginx reverse proxy
- API client with type definitions for users, devices, policies, gateways, and audit logs
- Admin pages for dashboard, users, devices, policies, g

backend/internal/user/service.go

@@ -0,0 +1,37 @@
+package user
+
+import (
+	"context"
+
+	"github.com/google/uuid"
+
+	"github.com/nexavpn/nexavpn/backend/internal/auth"
+)
+
+type Service struct {
+	repo Repository
+}
+
+func NewService(repo Repository) *Service {
+	return &Service{repo: repo}
+}
+
+func (s *Service) List(ctx context.Context) ([]User, error) {
+	return s.repo.List(ctx)
+}
+
+func (s *Service) Create(ctx context.Context, input CreateRequest) (User, error) {
+	passwordHash, err := auth.HashPassword(input.Password)
+	if err != nil {
+		return User{}, err
+	}
+	return s.repo.Create(ctx, input, passwordHash)
+}
+
+func (s *Service) SetActive(ctx context.Context, userID string, active bool) error {
+	id, err := uuid.Parse(userID)
+	if err != nil {
+		return err
+	}
+	return s.repo.SetActive(ctx, id, active)
+}