Use a custom JS audio player to be able to set the CSS on it so it fits in with the rest of the UI

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No files or tests are named in this issue. Start by locating where audio playback is implemented in the TypeScript frontend (look for audio element/player components and their CSS modules/scss). First inspect that component path to understand how the current player is rendered, then switch to a custom JS audio player and update styling entry points there. Done means the custom player is in use and its CSS can be controlled to match the rest of the UI, with build/test checks passing.

Written by the indexing model from the issue text.