whisper_main.py:
- Remove RobotEar.start_recording() and record_callback() which called
the nonexistent sd.start_stream() API (correct API is sd.InputStream).
These methods were never called by voice_main.py and contained a broken
sounddevice API call that would raise AttributeError (#2).
- Remove unused recording_buffer field
- Translate Chinese comment/docstring to English (#5)
voice_main.py:
- Move `import scipy.io.wavfile as wav` from inside get_audio_text()
function body to module top-level where all imports belong (#4 related)
- Sort imports: stdlib before third-party, local last
- Remove Chinese comment, replace with English equivalent
