The ui-wails -> ui rename deleted the fyne installer assets but left the
NSIS and WiX scripts pointing at client/ui/assets/netbird.ico, which broke
the Windows Installer CI job. Point both scripts at the Wails-side icon
(client/ui/build/windows/icon.ico) and restore banner.bmp into the new
build directory so the NSIS welcome/finish sidebar keeps rendering.
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.
