Meet2Notes 0.6.1

• Added simultaneous microphone and system-audio capture so video calls can
  record both sides of the conversation into one private local meeting.
• Added a clock-aligned 48 kHz mono mixer with per-input resampling, equal-gain
  headroom, gap preservation, and the same mixed frames for live transcription
  and the final WAV recording.
• Redesigned the New transcription source picker with independent microphone
  and system selections, persistent device choices, platform guidance, source
  availability checks, and separate live level meters.
• Preserved the single-source capture API while adding a bounded source_ids
  request for exactly one microphone/interface plus one system source.
• Improved capture failure handling for disconnected devices, silent Windows
  loopback outputs, pause/resume, partial stream startup, and cleanup on retry.
• Added cross-platform combined-capture and mixer tests plus detailed Windows,
  macOS, and Linux setup and troubleshooting documentation.