TUN-9863: Introduce Code Signing for Windows Builds

* TUN-9863: Introduce Code Signing for Windows Builds

This commit adds a signing step to the build script for windows binaries.
Since we package the MSI on Linux, this commit adds another CI step that depends on package-windows and signs all of the windows packages.

To do so, we use azuresigntool which relies on a certificate stored in Azure Vault.

Closes TUN-9863

.ci/scripts/windows/sign-msi.ps1

@@ -0,0 +1,26 @@
+# Sign Windows artifacts using azuretool
+# This script processes MSI files from the artifacts directory
+
+$ErrorActionPreference = "Stop"
+
+# Define paths
+$ARTIFACT_DIR = "artifacts"
+$TIMESTAMP_RFC3161 = "http://timestamp.digicert.com"
+
+Write-Host "Looking for Windows artifacts to sign in $ARTIFACT_DIR..."
+
+# Find all Windows MSI files
+$msiFiles = Get-ChildItem -Path $ARTIFACT_DIR -Filter "cloudflared-windows-*.msi" -ErrorAction SilentlyContinue
+
+if ($msiFiles.Count -eq 0) {
+    Write-Host "No Windows MSI files found in $ARTIFACT_DIR"
+    exit 1
+}
+
+Write-Host "Found $($msiFiles.Count) file(s) to sign:"
+foreach ($file in $msiFiles) {
+    Write-Host "Running azuretool sign for $($file.Name)"
+    azuresigntool.exe sign -kvu $env:KEY_VAULT_URL -kvi "$env:KEY_VAULT_CLIENT_ID" -kvs "$env:KEY_VAULT_SECRET" -kvc "$env:KEY_VAULT_CERTIFICATE" -kvt "$env:KEY_VAULT_TENANT_ID" -tr "$TIMESTAMP_RFC3161" -d "Cloudflare Tunnel Daemon" .\\$ARTIFACT_DIR\\$($file.Name)
+}
+
+Write-Host "Signing process completed"