feat: 新增 Frpc 一键启动与实时日志回显功能

新增一键启动/停止 Frpc 的命令及后端进程管理模块，支持生成配置文件、独立进程拉起、日志实时推送与退出事件通知。新增 Frpc 状态与日志类型定义，同步更新前端仪表盘逻辑以展示运行状态与实时日志。新增中英文启动失败提示文案，完善应用退出时自动终止 Frpc 子进程的逻辑。

src/i18n/locales/en-US.json

@@ -50,7 +50,8 @@
     "logEmpty": "No logs yet. Live logs will appear here once Frpc starts.",
     "logReady": "Frpilot is ready. Waiting for Frpc to start.",
     "logStarted": "Frpc {version} started",
-    "logStopped": "Frpc stopped"
+    "logStopped": "Frpc stopped",
+    "logStartFailed": "Failed to start Frpc: {message}"
   },
   "settings": {
     "title": "Settings",

src/i18n/locales/zh-CN.json

@@ -50,7 +50,8 @@
     "logEmpty": "暂无日志，启动 Frpc 后将在此显示实时日志",
     "logReady": "Frpilot 已就绪，等待启动 Frpc",
     "logStarted": "已启动 Frpc {version}",
-    "logStopped": "已停止 Frpc"
+    "logStopped": "已停止 Frpc",
+    "logStartFailed": "启动 Frpc 失败：{message}"
   },
   "settings": {
     "title": "设置",