v3.1.1

This patch release fixes 2 problems found in 3.1.0

Fixed

• Server → GPU video conversion now correctly detects NVENC. The capability
  check encoded a probe frame smaller than NVENC's minimum supported size, so it always
  failed and every conversion fell back to CPU, even on a GPU whose encoder works

• Package → the package reports its real version again. __version__ was not
  updated for the 3.1.0 release, so the version shown in the desktop launcher (and used
  to name the local data directory) was stale