Auris v1.1.2

Expose raw audio and add PCM->WAV helper

Add end-to-end raw audio support: the Auris transcription hook and Subscribe callbacks now receive a 4th `audio` argument (raw 16 kHz mono float32 PCM, nil on rare cache miss). Implement a Lua helper Auris.PCMToWAV(pcm) to wrap the raw PCM into a WAV container.

On the native side, add an audio cache (source/audio_cache.*) and store audio in auris_context before running transcription; lua_bindings.Poll now returns the audio binary as a third return value. Update the auris-discord submodule to optionally attach audio as a multipart WAV upload (build multipart body + content type), converting with Auris.PCMToWAV.

Docs and examples updated (API.md, README.md) to show audio usage and warn to guard the 4th arg. Bump Auris.VERSION to 1.1.2 and include a sample voice.wav file.