The composer's 📎 attach now takes audio as well as images:

* index.html: file input accept="image/*,audio/*"; the preview bar gains
  an <audio controls> element and a filename label alongside the image
  thumbnail; button relabelled "Attach media".
* app.js: `pendingImage` → `pendingMedia` carrying `{dataUrl, base64,
  kind, name}`. The picker classifies image vs audio from the MIME type
  (rejecting anything else), the preview shows a thumbnail for images and
  a mini player for audio, and the user bubble renders the same. Dispatch
  is unchanged — both image and audio ride the Ollama `images:[base64]`
  field because the backend's mtmd path auto-detects the media type from
  the bytes (no backend change needed).
* style.css: audio player + filename styling in the bar and in bubbles.

docs(readme): bump the stale Engine status badge v0.5.8 → v0.6.0.

Note: audio understanding is experimental upstream (llama.cpp flags it),
and the web path now matches the CLI capability for parity.