Icona dell'app: squircle verde con nota musicale

Creata un'icona coerente con la palette dell'app: squircle Apple-style
(corner radius ~22%), gradient verde Spotify -> verde scuro, nota
musicale (♫) bianca centrata con leggero glow, sottile highlight in
alto e bordo soft per definizione.

- assets/generate_icon.py: script PIL riproducibile, produce
  icon.png (master 1024) -> icon.iconset/ -> iconutil -> icon.icns
  (macOS) e icon.ico multi-size (Windows)
- assets/icon.png / icon.icns / icon.ico committati
- assets/icon.iconset/ in .gitignore (intermedio rigenerabile)
- build_macos.py: --icon assets/icon.icns se presente
- build_windows.py: --icon assets/icon.ico se presente

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

build_windows.py

@@ -99,14 +99,17 @@ def run_pyinstaller():
         if f.is_file() and f.suffix in (".exe", ""):
             add_binaries.extend(["--add-binary", f"{f};."])
 
+    icon_path = ROOT / "assets" / "icon.ico"
     cmd = [
         sys.executable, "-m", "PyInstaller",
         "--name", "MusicTools",
         "--windowed",
         "--onedir",
         "--noconfirm",
-        # Icona (se presente)
-        # "--icon", str(ROOT / "icon.ico"),
+    ]
+    if icon_path.exists():
+        cmd.extend(["--icon", str(icon_path)])
+    cmd.extend([
         # Web UI assets (HTML/CSS/JS) — usati da pywebview
         "--add-data", f"{ROOT / 'webui'};webui",
         # Hidden imports per pywebview (EdgeChromium su Windows)
@@ -121,7 +124,7 @@ def run_pyinstaller():
         *add_binaries,
         # Entry point
         str(ROOT / "main.py"),
-    ]
+    ])
 
     log(f"Comando: {' '.join(cmd[:10])}...")
     subprocess.run(cmd, check=True, cwd=str(ROOT))