chore: add Windows PowerShell version of RAUC key gen script

scripts/gen-rauc-signing-keys.ps1

@@ -0,0 +1,64 @@
+# Generate the RAUC signing-cert PAIR used to sign OS bundles.
+# Run ONCE per deployment. Requires OpenSSL in PATH (e.g. via Git for Windows,
+# choco install openssl, or winget install ShiningLight.OpenSSL).
+#
+# Outputs (written to ./rauc-signing/):
+#   ca-cert.pem        - embed in kiosk image at /etc/rauc/keyring.pem
+#   ca-key.pem         - KEEP OFFLINE. Only used to issue new signing certs.
+#   signing-cert.pem   - GitHub Actions secret BF_RAUC_SIGNING_CERT
+#   signing-key.pem    - GitHub Actions secret BF_RAUC_SIGNING_KEY
+
+param(
+    [string]$OutDir = ".\rauc-signing"
+)
+
+$ErrorActionPreference = "Stop"
+
+if (-not (Get-Command openssl -ErrorAction SilentlyContinue)) {
+    Write-Error "openssl not found in PATH. Install via: winget install ShiningLight.OpenSSL"
+    exit 1
+}
+
+if (Test-Path "$OutDir\ca-cert.pem") {
+    Write-Error "Refusing to overwrite existing keys at $OutDir - delete first if intentional"
+    exit 1
+}
+
+New-Item -ItemType Directory -Force -Path $OutDir | Out-Null
+Push-Location $OutDir
+
+try {
+    Write-Host "==> Generating CA (Ed25519, 10 year validity)"
+    openssl genpkey -algorithm ED25519 -out ca-key.pem
+    openssl req -new -x509 -days 3650 -key ca-key.pem `
+        -subj "/CN=BetterFrame RAUC CA" -out ca-cert.pem
+
+    Write-Host "==> Generating signing cert (Ed25519, 2 year validity)"
+    openssl genpkey -algorithm ED25519 -out signing-key.pem
+    openssl req -new -key signing-key.pem `
+        -subj "/CN=BetterFrame RAUC Signing" -out signing.csr
+    openssl x509 -req -in signing.csr -CA ca-cert.pem -CAkey ca-key.pem `
+        -CAcreateserial -days 730 -out signing-cert.pem
+
+    Remove-Item -Force signing.csr, ca-cert.srl -ErrorAction SilentlyContinue
+
+    Write-Host ""
+    Write-Host "==> Done. Next steps:"
+    Write-Host ""
+    Write-Host "1. Commit CA cert into repo:"
+    Write-Host "     Copy-Item $(Resolve-Path ca-cert.pem) ..\deploy\rauc\ca-cert.pem"
+    Write-Host "     git add deploy/rauc/ca-cert.pem"
+    Write-Host "     git commit -m 'chore(rauc): commit CA cert'"
+    Write-Host "     git push"
+    Write-Host ""
+    Write-Host "2. Set GitHub Actions secrets (Settings > Secrets > Actions):"
+    Write-Host "     BF_RAUC_SIGNING_CERT = contents of $(Resolve-Path signing-cert.pem)"
+    Write-Host "     BF_RAUC_SIGNING_KEY  = contents of $(Resolve-Path signing-key.pem)"
+    Write-Host ""
+    Write-Host "3. STORE ca-key.pem OFFLINE. Only needed to issue replacement signing certs."
+    Write-Host ""
+    Get-ChildItem | Format-Table Name, Length
+}
+finally {
+    Pop-Location
+}