Report TypeError raised inside a view as a Server error

[SAY-5]

Fixes #755.

A TypeError raised inside a view (from the view's own logic, not from parameter validation) was caught by the same handler that maps typeguard's argument checking to InvalidParamsError, so the caller got a 400 Invalid params response instead of a 500 Server error.

typeguard reports argument type mismatches as TypeCheckError (which is not a TypeError), so the view call is now wrapped in a narrower handler that only converts TypeCheckError to InvalidParamsError. A plain TypeError from the view body propagates and is reported as a Server error, while binding and annotated-metadata failures still map to Invalid params. Added a regression test in test_site.py.