fix: default ENABLE_NUGET to false for template safety

Template users should opt-in to NuGet publishing after configuring
NUGET_API_KEY secret, rather than failing on first release.

Made-with: Cursor

Author: Hongwei-MB

.github/workflows/ci.yml

@@ -39,7 +39,7 @@ env:
   DOTNET_CLI_TELEMETRY_OPTOUT: true
   NUKE_TELEMETRY_OPTOUT: true
   FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true
-  ENABLE_NUGET: 'true'
+  ENABLE_NUGET: 'false'
   NUGET_USE_OIDC: 'false'
   ENABLE_INSTALLERS: 'true'
   ENABLE_ANDROID: 'false'