When a workspace is created without an explicit content_language,
`data_get($data, 'content_language')` returns null, array_filter drops the key,
and the column falls back to its DB default of 'en'. So AI content and
notifications came out in English even when the app was running in another
locale.
Default to `app()->getLocale()` instead, so a new workspace inherits the user's
current language. An explicit content_language still wins.
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