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>

core/paths.py

@@ -0,0 +1,137 @@
+"""Risoluzione path per binari esterni (yt-dlp, ffmpeg).
+
+Quando l'app gira come bundle PyInstaller, i binari sono inclusi
+nella cartella del bundle. Altrimenti cerca nel sistema.
+
+Cross-platform: macOS e Windows.
+"""
+
+from __future__ import annotations
+
+import os
+import shutil
+import sys
+from pathlib import Path
+from typing import Optional
+
+_IS_WINDOWS = sys.platform == "win32"
+
+
+def _is_frozen() -> bool:
+    """True se stiamo girando come bundle PyInstaller."""
+    return getattr(sys, "frozen", False)
+
+
+def _bundle_dirs() -> list[Path]:
+    """Directories dove cercare i binari bundled (PyInstaller)."""
+    dirs = []
+    if _is_frozen():
+        # _MEIPASS: directory dove PyInstaller estrae i file
+        meipass = Path(getattr(sys, "_MEIPASS", ""))
+        if meipass.exists():
+            dirs.append(meipass)
+        # Directory dell'eseguibile
+        exe_dir = Path(sys.executable).parent
+        dirs.append(exe_dir)
+        # macOS: Contents/Frameworks/ (PyInstaller onedir .app)
+        if not _IS_WINDOWS:
+            frameworks = exe_dir.parent / "Frameworks"
+            if frameworks.exists():
+                dirs.append(frameworks)
+    return dirs
+
+
+def _exe(name: str) -> str:
+    """Aggiunge .exe su Windows."""
+    if _IS_WINDOWS and not name.endswith(".exe"):
+        return name + ".exe"
+    return name
+
+
+def find_ytdlp() -> str:
+    """Trova il path di yt-dlp.
+
+    Ordine di ricerca:
+    1. Bundle PyInstaller
+    2. Homebrew (macOS) / PATH comune (Windows)
+    3. Qualsiasi posizione nel PATH
+    """
+    name = _exe("yt-dlp")
+
+    # 1. Bundle
+    for d in _bundle_dirs():
+        candidate = d / name
+        if candidate.exists():
+            return str(candidate)
+
+    # 2. Percorsi noti per OS
+    if not _IS_WINDOWS:
+        brew = shutil.which("yt-dlp", path="/opt/homebrew/bin:/usr/local/bin")
+        if brew:
+            return brew
+
+    # 3. PATH generico
+    system = shutil.which("yt-dlp")
+    if system:
+        return system
+
+    msg = "yt-dlp non trovato. "
+    if _IS_WINDOWS:
+        msg += "Scaricalo da https://github.com/yt-dlp/yt-dlp/releases"
+    else:
+        msg += "Installalo con: brew install yt-dlp"
+    raise FileNotFoundError(msg)
+
+
+def find_ffmpeg_dir() -> Optional[str]:
+    """Trova la directory contenente ffmpeg e ffprobe.
+
+    Ordine di ricerca:
+    1. Bundle PyInstaller
+    2. Percorsi noti per OS
+    3. Qualsiasi posizione nel PATH
+    """
+    ffmpeg_name = _exe("ffmpeg")
+
+    # 1. Bundle
+    for d in _bundle_dirs():
+        if (d / ffmpeg_name).exists():
+            return str(d)
+
+    # 2. Percorsi noti
+    if _IS_WINDOWS:
+        # Posizioni comuni su Windows
+        for search in (
+            Path(os.environ.get("LOCALAPPDATA", "")) / "Programs" / "ffmpeg" / "bin",
+            Path("C:/ffmpeg/bin"),
+            Path(os.environ.get("ProgramFiles", "")) / "ffmpeg" / "bin",
+        ):
+            if (search / "ffmpeg.exe").exists():
+                return str(search)
+    else:
+        for search_path in ("/opt/homebrew/bin", "/usr/local/bin"):
+            if (Path(search_path) / "ffmpeg").exists():
+                return search_path
+
+    # 3. PATH generico
+    ffmpeg = shutil.which("ffmpeg")
+    if ffmpeg:
+        return str(Path(ffmpeg).parent)
+
+    return None
+
+
+def find_ffmpeg() -> Optional[str]:
+    """Ritorna il path completo di ffmpeg."""
+    d = find_ffmpeg_dir()
+    if d:
+        return str(Path(d) / _exe("ffmpeg"))
+    return None
+
+
+def find_ffprobe() -> Optional[str]:
+    """Ritorna il path completo di ffprobe."""
+    d = find_ffmpeg_dir()
+    if d:
+        return str(Path(d) / _exe("ffprobe"))
+    return None