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>

.gitignore

@@ -0,0 +1,36 @@
+# Python
+__pycache__/
+*.py[cod]
+*$py.class
+*.egg-info/
+.venv/
+venv/
+
+# OS
+.DS_Store
+Thumbs.db
+
+# IDE
+.vscode/
+.idea/
+*.swp
+
+# PyInstaller
+build/
+dist/
+*.spec
+bundle_bin/
+
+# App data — sensibili o specifici dell'utente
+config.json
+cookies.txt
+MUSICA/
+
+# Logs
+*.log
+.downloaded_tracks
+.upgraded_tracks
+
+# Claude
+.claude/
+Apri con claude-social.command