[client] UI refactor (#6069)

Refactor UI

---------

Co-authored-by: Eduard Gert <kontakt@eduardgert.de>
Co-authored-by: braginini <bangvalo@gmail.com>
Co-authored-by: Pascal Fischer <32096965+pascal-fischer@users.noreply.github.com>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: riccardom <riccardomanfrin@gmail.com>

client/ui/build/linux/desktop

@@ -0,0 +1,13 @@
+[Desktop Entry]
+Version=1.0
+Name=NetBird
+Comment=NetBird desktop client
+# The Exec line includes %u to pass the URL to the application
+Exec=/usr/local/bin/netbird-ui %u
+Terminal=false
+Type=Application
+Icon=netbird-ui
+Categories=Utility;
+StartupWMClass=netbird-ui
+
+