Folders conflicting with generated page routes

[tristan-mouchet]

There are a few folders that should be moved inside "app/ycode" to prevent conflicts with the generated app.

For example if users were to create a page with a "welcome" slug, opening the generated page would show the Ycode welcome page instead.

We might want to move the "api" folder too which might be more complex... or prevent any folder/page/cms item to use the "api" name as slug.