[client/ui] Finish ui-wails rename (import paths, fyne deps)

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.

.github/workflows/golang-test-linux.yml

@@ -154,7 +154,7 @@ jobs:
         run: git --no-pager diff --exit-code
 
       - name: Test
-        # Exclude client/ui-wails: its main.go uses //go:embed all:frontend/dist,
+        # Exclude client/ui: its main.go uses //go:embed all:frontend/dist,
         # which fails to compile until the frontend has been built. The Wails UI
         # has no Go-side unit tests, and its release pipeline runs `pnpm build`
         # before goreleaser.
@@ -162,7 +162,7 @@ jobs:
         # resolve; the grep then drops the broken package by path. Without -e,
         # go list aborts with empty stdout and `go test` falls back to the repo
         # root, which has no Go files.
-        run: CGO_ENABLED=1 GOARCH=${{ matrix.arch }} CI=true go test -tags devcert -exec 'sudo' -timeout 10m -p 1 $(go list -e ./... | grep -v -e /management -e /signal -e /relay -e /proxy -e /combined -e /client/ui-wails)
+        run: CGO_ENABLED=1 GOARCH=${{ matrix.arch }} CI=true go test -tags devcert -exec 'sudo' -timeout 10m -p 1 $(go list -e ./... | grep -v -e /management -e /signal -e /relay -e /proxy -e /combined -e /client/ui)
 
   test_client_on_docker:
     name: "Client (Docker) / Unit"