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/audit/service.go

@@ -0,0 +1,47 @@
+package audit
+
+import (
+	"context"
+	"encoding/json"
+
+	"github.com/google/uuid"
+)
+
+type Entry struct {
+	ActorUserID *uuid.UUID
+	EntityType  string
+	EntityID    *uuid.UUID
+	EventType   string
+	Status      string
+	Message     string
+	Metadata    map[string]any
+}
+
+type Repository interface {
+	Write(ctx context.Context, entry Entry) error
+	List(ctx context.Context, limit int) ([]map[string]any, error)
+}
+
+type Service struct {
+	repo Repository
+}
+
+func NewService(repo Repository) *Service {
+	return &Service{repo: repo}
+}
+
+func (s *Service) Record(ctx context.Context, entry Entry) error {
+	if entry.Metadata == nil {
+		entry.Metadata = map[string]any{}
+	}
+	return s.repo.Write(ctx, entry)
+}
+
+func (s *Service) List(ctx context.Context, limit int) ([]map[string]any, error) {
+	return s.repo.List(ctx, limit)
+}
+
+func MarshalMetadata(metadata map[string]any) []byte {
+	raw, _ := json.Marshal(metadata)
+	return raw
+}