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/ipam/service.go

@@ -0,0 +1,26 @@
+package ipam
+
+import (
+	"fmt"
+	"net/netip"
+)
+
+type Service struct{}
+
+func NewService() *Service {
+	return &Service{}
+}
+
+func (s *Service) Allocate(cidr string, offset int) (string, error) {
+	prefix, err := netip.ParsePrefix(cidr)
+	if err != nil {
+		return "", err
+	}
+
+	address := prefix.Addr().Next()
+	for i := 1; i < offset; i++ {
+		address = address.Next()
+	}
+
+	return fmt.Sprintf("%s/32", address.String()), nil
+}