feat(installer): add finish screen with launch-app checkbox to Windows MSI

Adds WixUI_Minimal UI to the WiX installer so users see a proper
Welcome → Progress → Finish wizard. The finish screen includes a
pre-ticked "Launch Open CAD Studio" checkbox; clicking Finish with
it checked starts the application immediately after the installer closes.

Also updates the light.exe invocation in release.yml to include
-ext WixUIExtension, which is required to link the WixUI dialogs.

https://claude.ai/code/session_01DFVSKgViFaxEjZD2KsTdtt

.github/workflows/release.yml

@@ -138,7 +138,7 @@ jobs:
             $wxsPath `
             -out $wixObj
           if ($LASTEXITCODE -ne 0) { throw "candle failed" }
-          & $light $wixObj -out $msiPath
+          & $light $wixObj -ext WixUIExtension -out $msiPath
           if ($LASTEXITCODE -ne 0) { throw "light failed" }
 
       - name: Sign MSI installer (Azure Trusted Signing)