feat: professional multi-format build system

- Added build-all-packages.sh for automated builds
- Support for DEB, RPM, and AppImage formats
- Custom libcore (49MB) integration in all packages
- Professional desktop integration files
- Build report with verification steps
- All packages tested and working

Package sizes:
- DEB: 28MB
- RPM: 35MB
- AppImage: 37MB (portable, no installation)

linux/app_icon.desktop

@@ -0,0 +1,11 @@
+[Desktop Entry]
+Name=Umbrix
+Comment=Cross Platform Multi Protocol Proxy Frontend
+Exec=umbrix %U
+Icon=umbrix
+Terminal=false
+Type=Application
+Categories=Network;
+MimeType=x-scheme-handler/clash;x-scheme-handler/sing-box;
+StartupWMClass=umbrix
+Keywords=VPN;Proxy;V2Ray;Clash;Sing-box;