Port IPv6 overlay support (#5631) into the Wails UI:
- Add DisableIPv6 config toggle to Settings (NetworkTab + services)
- Filter ::/0 alongside 0.0.0.0/0 as an exit-node route
- Suppress duplicate v6 default-route notifications in tray
Follow-up to the rename commit: the previous commit moved the files but
the post-mv string substitutions (Go imports, frontend bindings, CI
config paths) were not re-staged so they slipped through. This commit
applies those edits and removes the fyne dependencies from go.mod/go.sum
now that the legacy fyne UI is gone.
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.
