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>

.github/workflows/build.yml

@@ -0,0 +1,59 @@
+name: Build MusicDownload
+
+on:
+  workflow_dispatch:  # Lancia manualmente da GitHub
+  push:
+    tags:
+      - 'v*'  # Builda automaticamente sui tag (es. v1.0.0)
+
+jobs:
+  build-macos:
+    runs-on: macos-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+
+      - name: Install dependencies
+        run: |
+          pip install -r requirements.txt
+          pip install pyinstaller
+
+      - name: Install ffmpeg
+        run: brew install ffmpeg
+
+      - name: Build app
+        run: python build_macos.py
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: MusicDownload-macOS
+          path: dist/MusicDownload.app
+          compression-level: 9
+
+  build-windows:
+    runs-on: windows-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+
+      - name: Install dependencies
+        run: |
+          pip install -r requirements.txt
+          pip install pyinstaller
+
+      - name: Build app
+        run: python build_windows.py
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: MusicDownload-Windows
+          path: dist/MusicDownload
+          compression-level: 9