fix: polish UX error handling across views (FINAL-01)

- AppDetails: replace alert() with dismissible toast, add error feedback
  for start/stop/restart/uninstall actions
- GoalDetail: add error toast for install failures instead of silent catch
- Apps: add loading skeleton when WebSocket data hasn't arrived yet
- Add appDetails.noLaunchUrl i18n key

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

neode-ui/src/locales/en.json

@@ -554,7 +554,8 @@
     "notFoundTitle": "App Not Found",
     "notFoundMessage": "The requested application could not be found",
     "installed": "Installed",
-    "channels": "Channels"
+    "channels": "Channels",
+    "noLaunchUrl": "No launch URL available for this app yet"
   },
   "containerDetails": {
     "back": "Back",