Microphone button in the chat composer and in free-text steps. The browser
records 16 kHz mono WAV (no server-side ffmpeg), /me/{token}/stt transcribes,
the text lands in the field for the patient to check and edit — never sent
automatically, so safety and scrub() apply on send. Hidden when the server has
voice input off or the browser lacks a microphone API. nginx: 4 MB body limit.
Refs #117
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
