[client/ui] Replace fyne UI with Wails (rename ui-wails to ui)

Removes the legacy fyne-based client/ui implementation and renames the
Wails replacement (client/ui-wails) to take its place at client/ui. Go
imports, frontend bindings, CI workflows, goreleaser configs and the
windows .syso icon path are updated to follow the rename.

client/ui/build/linux/netbird-ui.desktop

@@ -0,0 +1,10 @@
+[Desktop Entry]
+Type=Application
+Name=netbird-ui
+Exec=env WEBKIT_DISABLE_DMABUF_RENDERER=1 netbird-ui
+Icon=netbird-ui
+Categories=Development;
+Terminal=false
+Keywords=wails
+Version=1.0
+StartupNotify=false