fix: Resolve macOS cross-compilation issues in unified release

- Disable old unified-build.yml workflow (was causing conflicts)
- Create new unified-release.yml with proper platform separation
- macOS builds now run on macOS runners (fixes cross-compilation)
- Linux and Windows builds use Ubuntu with cross-compilation
- Separate build jobs for each platform to prevent cancellation
- Rename workflow to indicate cross-platform support

Platform matrix:
✅ Linux x64: Ubuntu runner (native)
✅ Windows x64: Ubuntu runner (cross-compile)
✅ macOS x64/ARM64: macOS runners (native)
✅ Android: Ubuntu runner (native)
✅ Backend: Ubuntu runner (native)

Fixes macOS build failures and prevents other builds from being canceled!

.github/workflows/unified-build.yml

@@ -1,14 +1,6 @@
-name: Unified Build and Deploy
+name: Unified Linux Build and Deploy (DISABLED - use unified-release.yml)
 
 on:
-  push:
-    branches:
-      - '**'
-    tags:
-      - 'v*'
-  pull_request:
-    branches:
-      - '**'
   workflow_dispatch:
     inputs:
       force_release: