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/config.py

@@ -0,0 +1,64 @@
+"""Gestione configurazione persistente (JSON)."""
+
+import json
+import os
+import sys
+from pathlib import Path
+
+VERSION = "v1.0"
+
+
+def _get_config_dir() -> Path:
+    """Ritorna la directory per config.json.
+
+    Frozen (bundle PyInstaller):
+    - macOS:   ~/Library/Application Support/MusicDownload/
+    - Windows: %APPDATA%/MusicDownload/
+    Dev (non frozen):
+    - directory del progetto
+    """
+    if getattr(sys, "frozen", False):
+        if sys.platform == "win32":
+            base = Path(os.environ.get("APPDATA", Path.home()))
+        else:
+            base = Path.home() / "Library" / "Application Support"
+        config_dir = base / "MusicDownload"
+        config_dir.mkdir(parents=True, exist_ok=True)
+        return config_dir
+    return Path(__file__).resolve().parent.parent
+
+
+CONFIG_PATH = _get_config_dir() / "config.json"
+
+# Default: i path relativi al progetto (se non frozen)
+_project_dir = Path(__file__).resolve().parent.parent
+
+DEFAULTS = {
+    "client_id": "",
+    "client_secret": "",
+    "bitrate": "320K",
+    "hq_threshold": 310,
+    "cookies_path": str(_project_dir / "cookies.txt"),
+    "output_dir": str(_project_dir / "MUSICA"),
+    "theme": "dark",
+}
+
+
+def load_config() -> dict:
+    """Carica la configurazione da config.json, con fallback ai default."""
+    config = dict(DEFAULTS)
+    if CONFIG_PATH.exists():
+        try:
+            with open(CONFIG_PATH, "r", encoding="utf-8") as f:
+                stored = json.load(f)
+            config.update(stored)
+        except (json.JSONDecodeError, OSError):
+            pass
+    return config
+
+
+def save_config(config: dict) -> None:
+    """Salva la configurazione su config.json."""
+    CONFIG_PATH.parent.mkdir(parents=True, exist_ok=True)
+    with open(CONFIG_PATH, "w", encoding="utf-8") as f:
+        json.dump(config, f, indent=2, ensure_ascii=False)