feat: add automated WireGuard runtime installation for Windows desktop client with bundled MSI installer

Add install-runtime command to tunnel-helper for automated WireGuard installation on Windows. Download and bundle official WireGuard MSI during build process with automatic version discovery from wireguard.com.

Add ensure_windows_runtime_installed checks before connect/disconnect operations. Implement install_windows_runtime with UAC elevation prompt and install_windows_runtime_direct for MS

.gitea/workflows/windows-desktop-client.yml

@@ -134,4 +134,5 @@ jobs:
           path: |
             desktop-client/src-tauri/target/x86_64-pc-windows-msvc/release/nexavpn-desktop.exe
             desktop-client/src-tauri/bundled/windows-x64/nexavpn-tunnel-helper.exe
+            desktop-client/src-tauri/bundled/windows-x64/wireguard-installer.msi
           if-no-files-found: error