I need to translate everything on my MSM sites into different languages. I notice that a lot of general error messages such as "The username you chose is not available" appear in the files in the folder /system/expressionengine/language/xyz
however there are thousands of lines of phrases, most of which appear in the control panel only. How can I tell which phrases appear in the front end so I can translate them, without having to laboriously try to trigger each message or guess where they are used? I found language packs for German, French, Spanish but not Italian or Polish.
EE version 2.9.2