feat(settings): add first-run confirmation dialogs for proxy and usage features

Prevent accidental activation of advanced features by showing a one-time
info dialog. Once confirmed, the flag is persisted in settings.json and
the dialog never appears again.

- Proxy: confirmation when toggling proxy server ON for the first time
- Usage: confirmation when enabling usage query inside UsageScriptModal
- Enhanced ConfirmDialog with "info" variant (blue icon + default button)
- Added i18n translations for zh, en, ja

src-tauri/src/settings.rs

@@ -190,6 +190,12 @@ pub struct AppSettings {
     /// 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,
+    /// User has confirmed the local proxy first-run notice
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub proxy_confirmed: Option<bool>,
+    /// User has confirmed the usage query first-run notice
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub usage_confirmed: Option<bool>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub language: Option<String>,
 
@@ -266,6 +272,8 @@ impl Default for AppSettings {
             launch_on_startup: false,
             silent_startup: false,
             enable_local_proxy: false,
+            proxy_confirmed: None,
+            usage_confirmed: None,
             language: None,
             visible_apps: None,
             claude_config_dir: None,