docs: add macOS build and packaging instructions

- Add detailed macOS build procedure for Electron app
- Include instructions for Intel and Universal builds
- Add code signing and notarization requirements
- Document running instructions for .app, .dmg, and .zip formats
- Add security warning handling instructions

BUILDING.md

@@ -236,21 +236,75 @@ docker run -d \
    - AppImage: `dist-electron-packages/TimeSafari-x.x.x.AppImage`
    - DEB: `dist-electron-packages/timesafari_x.x.x_amd64.deb`
 
+### macOS Build
+
+1. Build the electron app in production mode:
+
+   ```bash
+   npm run build:electron-prod
+   ```
+
+2. Package the Electron app for macOS:
+
+   ```bash
+   # For Intel Macs
+   npm run electron:build-mac
+
+   # For Universal build (Intel + Apple Silicon)
+   npm run electron:build-mac-universal
+   ```
+
+3. The packaged applications will be in `dist-electron-packages/`:
+   - `.app` bundle: `TimeSafari.app`
+   - `.dmg` installer: `TimeSafari-x.x.x.dmg`
+   - `.zip` archive: `TimeSafari-x.x.x-mac.zip`
+
+### Code Signing and Notarization (macOS)
+
+For public distribution on macOS, you need to code sign and notarize your app:
+
+1. Set up environment variables:
+   ```bash
+   export CSC_LINK=/path/to/your/certificate.p12
+   export CSC_KEY_PASSWORD=your_certificate_password
+   export APPLE_ID=your_apple_id
+   export APPLE_ID_PASSWORD=your_app_specific_password
+   ```
+
+2. Build with signing:
+   ```bash
+   npm run electron:build-mac
+   ```
+
 ### Running the Packaged App
 
-- AppImage: Make executable and run
+- **Linux**:
+  - AppImage: Make executable and run
+    ```bash
+    chmod +x dist-electron-packages/TimeSafari-*.AppImage
+    ./dist-electron-packages/TimeSafari-*.AppImage
+    ```
+  - DEB: Install and run
+    ```bash
+    sudo dpkg -i dist-electron-packages/timesafari_*_amd64.deb
+    timesafari
+    ```
 
-  ```bash
-  chmod +x dist-electron-packages/TimeSafari-*.AppImage
-  ./dist-electron-packages/TimeSafari-*.AppImage
-  ```
+- **macOS**:
+  - `.app` bundle: Double-click `TimeSafari.app` in Finder
+  - `.dmg` installer:
+    1. Double-click the `.dmg` file
+    2. Drag the app to your Applications folder
+    3. Launch from Applications
+  - `.zip` archive:
+    1. Extract the `.zip` file
+    2. Move `TimeSafari.app` to your Applications folder
+    3. Launch from Applications
 
-- DEB: Install and run
-
-  ```bash
-  sudo dpkg -i dist-electron-packages/timesafari_*_amd64.deb
-  timesafari
-  ```
+  Note: If you get a security warning when running the app:
+  1. Right-click the app
+  2. Select "Open"
+  3. Click "Open" in the security dialog
 
 ### Development Testing