fix: CRUD endpoint return format - remove json.dumps, use widgettype format

wwwroot/api/receivables_create.dspy

@@ -1,7 +1,6 @@
 #!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 """Receivable create API"""
-import json, uuid, time
 
 result = {'widgettype': 'Message', 'options': {'title': 'Error', 'message': 'Invalid request', 'type': 'error'}}
 
@@ -35,4 +34,4 @@ try:
 except Exception as e:
     result['options'] = {'title': 'Error', 'message': f'创建失败: {str(e)}', 'type': 'error'}
 
-return json.dumps(result, ensure_ascii=False)
+return result

wwwroot/api/receivables_delete.dspy

@@ -1,7 +1,6 @@
 #!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 """Receivable delete API"""
-import json
 
 result = {'widgettype': 'Message', 'options': {'title': 'Error', 'message': 'Invalid request', 'type': 'error'}}
 
@@ -22,4 +21,4 @@ try:
 except Exception as e:
     result['options'] = {'title': 'Error', 'message': f'删除失败: {str(e)}', 'type': 'error'}
 
-return json.dumps(result, ensure_ascii=False)
+return result

wwwroot/api/receivables_update.dspy

@@ -1,7 +1,6 @@
 #!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 """Receivable update API"""
-import json, time
 
 result = {'widgettype': 'Message', 'options': {'title': 'Error', 'message': 'Invalid request', 'type': 'error'}}
 
@@ -36,4 +35,4 @@ try:
 except Exception as e:
     result['options'] = {'title': 'Error', 'message': f'更新失败: {str(e)}', 'type': 'error'}
 
-return json.dumps(result, ensure_ascii=False)
+return result