fix: bypass YouTube bot detection on HF Spaces

chore: add Dockerfile for HF Spaces deploy, CORS env var support

feat: 7 UI/UX improvements — BPM, waveform, chord chart, fret hints, confidence opacity, consistent key badge, 3-octave piano

Revert "feat: auto-detect guitar/keyboard from title keywords + key + spectral features"

feat: auto-detect guitar/keyboard from title keywords + key + spectral features

feat: show song title from YouTube metadata

fix: auto-load .env for HF_TOKEN, add .env to gitignore

feat: audio playback with moving playhead, auto segment tracking, click-to-seek

feat: 30s timeline bars, stagger animation, fix use_return_dict deprecation, suppress audioread warning

feat: YouTube URL support + fix Tailwind v4 CSS + fix CORS ports

fix: correct confidence averaging in merge_segments, add 50MB upload limit

feat: FastAPI /analyze — MERT boundaries + KS key detection + guitar info