feat: global right-click control + topic tree context menu

- UseContextMenu composable: global right-click prevention
  - PROD: prevent default browser context menu everywhere
  - DEV: allow native context menu for debugging
- ContextMenu component: reusable custom right-click menu
- TopicTree: right-click nodes for copy topic / subscribe / unsubscribe / filter
  - Copy topic to clipboard
  - Subscribe with QoS 0/1/2
  - Unsubscribe with confirmation
  - Filter by topic

src/App.vue

@@ -1,5 +1,8 @@
 <script setup lang="ts">
-import AppLayout from "./components/AppLayout.vue";
+import { useContextMenuController } from "./composables/useContextMenu"
+import AppLayout from "./components/AppLayout.vue"
+
+useContextMenuController()
 </script>
 
 <template>