feat(claude-desktop): add 3P provider switching with proxy gateway

Adds a new ClaudeDesktop AppType that writes Claude Desktop's third-party
inference profile under configLibrary/, sharing _meta.json with other
launchers (Ollama-compatible) so cc-switch can coexist with them.

Two switch modes:
- direct: provider already exposes claude-* / anthropic/claude-* model
  ids on Anthropic Messages, Claude Desktop connects to it directly.
- proxy: cc-switch's local proxy acts as the inference gateway,
  presenting only claude-* route names to Claude Desktop and mapping
  them to real upstream models. Required after Anthropic restricted
  Claude Desktop to claude-family ids.

Backend:
- New module claude_desktop_config with snapshot/rollback, official seed
  bypass, /claude-desktop/v1/{models,messages} routes, and a single
  source of truth for default proxy routes.
- Gateway token persisted in SQLite, validated on every proxied request.
- get_claude_desktop_status surfaces drift signals (stale models,
  missing routes, proxy stopped, base URL mismatch, missing token).

Frontend:
- Slim ClaudeDesktopProviderForm independent from ProviderForm,
  controlled by a top-level appId guard.
- ProviderList banner consumes the status query (5s polling) and
  renders actionable diagnostics.
- ClaudeDesktopRouteToggle in the header to start/stop the local
  gateway without touching takeover state.
- Three-locale i18n synchronised.

src-tauri/src/commands/proxy.rs

@@ -15,6 +15,24 @@ pub async fn start_proxy_server(
     state.proxy_service.start().await
 }
 
+/// 停止代理服务器（仅停止服务，不恢复/清理 Live 接管状态）
+#[tauri::command]
+pub async fn stop_proxy_server(state: tauri::State<'_, AppState>) -> Result<(), String> {
+    let takeover = state.proxy_service.get_takeover_status().await?;
+    if takeover.claude
+        || takeover.codex
+        || takeover.gemini
+        || takeover.opencode
+        || takeover.openclaw
+    {
+        return Err(
+            "仍有应用处于代理接管状态，请先在设置中关闭对应应用接管后再停止本地路由。".to_string(),
+        );
+    }
+
+    state.proxy_service.stop().await
+}
+
 /// 停止代理服务器（恢复 Live 配置）
 #[tauri::command]
 pub async fn stop_proxy_with_restore(state: tauri::State<'_, AppState>) -> Result<(), String> {