Audio smoke test

WAV → MP3 conversion + media-page audio embed

3-second sine wave at 440Hz — Day 6 audio smoke test (synthetic WAV → MP3 via ffmpeg).

If you can play this audio above, the full WAV → MP3 → public/audio.mp3 → <audio controls> path works end-to-end.

Source: synthetic 3s sine wave. ffmpeg converted WAV (~96KB) to MP3 (~6KB at 192kbps).