feat(desktop-client): add settings window and switch default API to production

- Open a dedicated settings BrowserWindow with general / login / diagnostics / about tabs
- Persist openAtLogin and keepRunningInBackground via desktop-settings.json; hide main window instead of quitting when background mode is on
- Default API base URL now points to api.shengxintui.com; LoginView and SettingsView share a single constant
- Restore wangyihao session cookies on probe and silent refresh, and accept the legacy http://mp.163.com console origin
- Drop the standalone diagnostics view in favor of the settings tab

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/desktop-client/src/renderer/env.d.ts

@@ -11,6 +11,11 @@ import type { DesktopRuntimeSnapshot } from "./types";
 export {};
 
 declare global {
+  interface DesktopAppSettings {
+    openAtLogin: boolean;
+    keepRunningInBackground: boolean;
+  }
+
   interface Window {
     desktopBridge: {
       app: {
@@ -40,6 +45,9 @@ declare global {
         listPublishTasks(params?: ListDesktopPublishTasksParams): Promise<DesktopPublishTaskListResponse>;
         retryPublishTask(taskId: string): Promise<CreatePublishJobResponse>;
         openExternalUrl(url: string): Promise<null>;
+        openSettingsWindow(): Promise<null>;
+        getAppSettings(): Promise<DesktopAppSettings>;
+        setAppSetting(key: keyof DesktopAppSettings, value: boolean): Promise<DesktopAppSettings>;
         syncRuntimeSession(session: DesktopRuntimeSessionSyncRequest | null): Promise<null>;
         releaseRuntimeSession(revoke?: boolean): Promise<null>;
         setWindowMode(mode: "login" | "main", request?: {