feat(settings): add enableLocalProxy toggle to gate main page proxy UI

New users often accidentally trigger ProxyToggle/FailoverToggle on the
main page. Add a settings toggle (default off) so the proxy controls
only appear when explicitly enabled. The proxy service start/stop in
settings remains independent of this visibility flag.

src-tauri/src/settings.rs

@@ -187,6 +187,9 @@ pub struct AppSettings {
     /// 静默启动（程序启动时不显示主窗口，仅托盘运行）
     #[serde(default)]
     pub silent_startup: bool,
+    /// 是否在主页面启用本地代理功能（默认关闭）
+    #[serde(default)]
+    pub enable_local_proxy: bool,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub language: Option<String>,
 
@@ -262,6 +265,7 @@ impl Default for AppSettings {
             skip_claude_onboarding: false,
             launch_on_startup: false,
             silent_startup: false,
+            enable_local_proxy: false,
             language: None,
             visible_apps: None,
             claude_config_dir: None,