feat: trigger actual Steam desktop login window via protocol handler for native account addition

frontend/electron/main.ts

@@ -505,6 +505,15 @@ ipcMain.handle('get-server-users', async () => { initBackend(); return backend ?
 ipcMain.handle('switch-account', async (event, loginName: string) => await handleSwitchAccount(loginName));
 ipcMain.handle('open-external', (event, url: string) => shell.openExternal(url));
 
+ipcMain.handle('open-steam-app-login', async () => {
+  console.log('[SteamClient] Triggering desktop login window...');
+  // Force Steam to show login window. 
+  // steam://open/login is the protocol for this.
+  const command = process.platform === 'win32' ? 'start steam://open/login' : 'xdg-open steam://open/login';
+  exec(command);
+  return true;
+});
+
 ipcMain.handle('open-steam-login', async (event, expectedSteamId: string) => {
   const loginSession = session.fromPartition('persist:steam-login');
   // Removed: automatic clearStorageData to allow cookie persistence

frontend/electron/preload.ts

@@ -10,6 +10,7 @@ contextBridge.exposeInMainWorld('electronAPI', {
   revokeAccountAccess: (steamId: string, targetSteamId: string) => ipcRenderer.invoke('revoke-account-access', steamId, targetSteamId),
   revokeAllAccountAccess: (steamId: string) => ipcRenderer.invoke('revoke-all-account-access', steamId),
   openExternal: (url: string) => ipcRenderer.invoke('open-external', url),
+  openSteamAppLogin: () => ipcRenderer.invoke('open-steam-app-login'),
   openSteamLogin: (steamId: string) => ipcRenderer.invoke('open-steam-login', steamId),
   
   // Server Config & Auth