The discovery pool synthesizes deezer popularity onto a 0-100 score (base 45 + bonuses, capped at 100), but _get_popularity_thresholds had deezer on the raw-rank scale (500000/100000). So Popular Picks' 'popularity >= 500000' matched nothing — empty for every deezer-primary user — while Hidden Gems' '< 100000' caught the whole pool. Deezer thresholds now sit on the 0-100 scale (60/50, like Spotify's 60/40). Tested.
