feat(auth): backup settings file before auth modification

- Add backupSettingsFile() utility to create .orig backup before modifying settings
- Update success message to indicate backup was created
- Sync i18n translations for all supported languages
- Update documentation to reflect the change

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

packages/cli/src/ui/auth/useAuth.ts

@@ -35,6 +35,7 @@ import {
   CodingPlanRegion,
   CODING_PLAN_ENV_KEY,
 } from '../../constants/codingPlan.js';
+import { backupSettingsFile } from '../../utils/settingsUtils.js';
 
 export type { QwenAuthState } from '../hooks/useQwenAuth.js';
 
@@ -304,6 +305,10 @@ export const useAuthCommand = (
         // Get persist scope
         const persistScope = getPersistScopeForModelSelection(settings);
 
+        // Backup settings file before modification
+        const settingsFile = settings.forScope(persistScope);
+        backupSettingsFile(settingsFile.path);
+
         // Store api-key in settings.env (unified env key)
         settings.setValue(persistScope, `env.${CODING_PLAN_ENV_KEY}`, apiKey);
 
@@ -384,7 +389,7 @@ export const useAuthCommand = (
           {
             type: MessageType.INFO,
             text: t(
-              'Authenticated successfully with {{region}}. API key is stored in settings.env.',
+              'Authenticated successfully with {{region}}. API key and model configs saved to settings.json (backed up).',
               { region: regionName },
             ),
           },