The XEmbed tray (panel) can come up after the autostarted UI on minimal
WMs, so the single startup probe added in #6320 could miss a tray that
appears a second or two later, leaving the icon silently absent. Re-probe
for a ~10s grace period in a goroutine, claiming the watcher as soon as a
tray shows up; back off cleanly if none ever appears (headless/Wayland).
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.
