Enhance Windows installer build process by adding BMP generation for installer assets and updating package dependencies. The build script now includes a step to generate installer header and sidebar images, and the package.json has been updated to include the 'sharp' library for image processing.

Author: staindart

.gitignore

@@ -8,6 +8,10 @@ node_modules/
 dist/
 web-build/
 releases/
+
+# NSIS installer BMPs generated from assets/images/installer*.svg (windows/generate-installer-bmps.cjs)
+windows/installerHeader.bmp
+windows/installerSidebar.bmp
 expo-env.d.ts
 
 # Native