Initial commit: MusicDownload con UI pywebview

- Frontend HTML/CSS/JS in webui/ (stile Spotify-like, hero gradient, modal blur)
- API bridge JS<->Python in api/bridge.py
- Core invariato: downloader yt-dlp, upgrader, spotify client, config
- Build scripts macOS (WebKit) e Windows (EdgeChromium)
- .gitignore esclude credenziali (config.json, cookies.txt) e artefatti build

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Vibes_List.txt

@@ -0,0 +1,5 @@
+https://open.spotify.com/intl-it/album/3lgCqbQpmLscSRuWVMT5wS?si=UPiqK8smRgO_1JAAiZTrYg
+https://open.spotify.com/intl-it/album/3pGb3m5KA1Y3gCVT6leCL3?si=Cj_OrTE5QAiEnwMD63EunA
+https://open.spotify.com/intl-it/album/2ewhdpODXqoB0fXIKfq4u2?si=e2N7jWHiTWGiudHHMJNHHQ
+https://open.spotify.com/intl-it/album/2xGfPfmx6faZUr9IaKEiSG?si=2Q-qMwWCTp-Yp7RIfhE2Ig
+https://open.spotify.com/intl-it/album/43pKffJweYUVwEYcHPIfox?si=2E8IoUmOQp-cgsCujVBPMQ