更新配置文件，重构工作流管理逻辑，调整国际化文件文职，优化图像生成和文本转语音服务的工作流解析，确保默认工作流配置必填，调整前端工作流选择逻辑。

config.example.yaml

@@ -23,7 +23,16 @@ tts:
 
 # ==================== Image Generation Configuration ====================
 image:
-  default: image_default.json
+  # Required: Default workflow to use (no fallback)
+  # Options: runninghub/image_default.json (recommended, no local setup)
+  #          selfhost/image_default.json (requires local ComfyUI)
+  default_workflow: runninghub/image_default.json
+  
+  # Local ComfyUI configuration (required if using selfhost workflows)
   comfyui_url: http://127.0.0.1:8188
+  
+  # RunningHub cloud configuration (required if using runninghub workflows)
   runninghub_api_key: ""
+  
+  # Image prompt prefix (optional)
   prompt_prefix: "Pure white background, minimalist illustration, matchstick figure style, black and white line drawing, simple clean lines"