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/auth/hash.go

@@ -0,0 +1,11 @@
+package auth
+
+import (
+	"crypto/sha256"
+	"encoding/base64"
+)
+
+func base64Hash(value string) string {
+	sum := sha256.Sum256([]byte(value))
+	return base64.RawURLEncoding.EncodeToString(sum[:])
+}