This commit adds a `panicTrace` function to be used as a drop-in
replacement of the `panic` function, with the difference that we
wrap the error in a `WithStacktrace` error, to be later caught
and logged.

This allows us to have only one single (static) map which will be
treated by GHC as a CAF.

We do that thanks to a new typeclass method for
the `MonadJobStatus` called `noJobHandle`.

This commit modifies the backend code to convert the input CSV into an
`NgramsList`, so that we can reuse the JSON API for the upload.

it also brings the CSV and JSON APIs closer in look.
Temporarily disable the `importCsvFile` function.