fix(icon): 🐛 fix app icon not displaying on macOS when running via npx (#8)

- Add `public/icons/` to npm package files to include icons in published package
- Add `getIconPath()` function to intelligently locate icon files across different run modes (dev/npx/packaged)
- Use `nativeImage` API for better icon loading with proper error handling
- Use PNG format for non-packaged mode as nativeImage has poor .icns/.ico support
- Add dedicated macOS PNG icons with transparent margins for Dock magnification effect
- Set Dock icon explicitly on macOS using `app.dock.setIcon()`
- Add window title 'MarkPDFdown'
- Add icons to extraResources for electron-builder packaging

Co-authored-by: Claude <noreply@anthropic.com>

Author: jorben

package.json

@@ -15,6 +15,7 @@
   "files": [
     "bin/",
     "dist/",
+    "public/icons/",
     "src/core/infrastructure/db/migrations/",
     "src/core/infrastructure/db/schema.prisma"
   ],
@@ -63,6 +64,10 @@
         "filter": [
           "**/*.sql"
         ]
+      },
+      {
+        "from": "public/icons",
+        "to": "icons"
       }
     ],
     "asarUnpack": [