feat: initial MQTT v5 debugging tool

- Tauri v2 + Vue 3 + TypeScript + Element Plus
- Connection management (CRUD + enable/disable/test)
- Preset system with {{variable}} placeholders
- Dashboard with live message scrolling + topic tree
- Payload inspector (JSON/Hex/Base64/Plain)
- Protocol-level logging (file + UI dual channel)
- Global variable manager with localStorage persistence
- MQTT v5 property support (user properties, content type, etc.)
- SubAck result tracking with subscribe_tracked API

package.json

@@ -0,0 +1,26 @@
+{
+  "name": "mqttx",
+  "private": true,
+  "version": "0.1.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "vue-tsc --noEmit && vite build",
+    "preview": "vite preview",
+    "tauri": "tauri"
+  },
+  "dependencies": {
+    "@element-plus/icons-vue": "^2.3.2",
+    "@tauri-apps/api": "^2",
+    "@tauri-apps/plugin-opener": "^2",
+    "element-plus": "^2.14.4",
+    "vue": "^3.5.13"
+  },
+  "devDependencies": {
+    "@tauri-apps/cli": "^2",
+    "@vitejs/plugin-vue": "^6.0.7",
+    "typescript": "~6.0.3",
+    "vite": "^8.0.16",
+    "vue-tsc": "^3.3.5"
+  }
+}