Add Dify integration and enhance workflow node specifications

- Introduce new fields `dify_api_url` and `dify_api_key` in `AssistantConfig` for Dify API integration.
- Update `requirements.txt` to include `dify-client-python` for Dify SDK support.
- Modify `config_resolver` to handle Dify connection information.
- Add a new `globalNode` type in workflow specifications to provide unified settings across workflows.
- Enhance node specifications with additional constraints and default values for better configuration management.
- Update frontend components to support the new `globalNode` type and its properties, improving workflow editor functionality.

backend/services/config_resolver.py

@@ -139,6 +139,8 @@ async def resolve_runtime_config(
         # workflow 图:仅 workflow 类型非空,引擎据此启用图驱动对话
         graph=(assistant.graph or {}) if assistant.type == "workflow" else {},
         # 外部托管类型连接信息(DB 存真 key,直接注入)
+        dify_api_url=str(_value(agent_resource, "apiUrl", assistant.api_url)),
+        dify_api_key=_secret(agent_resource, "apiKey", assistant.api_key),
         fastgpt_api_url=str(_value(agent_resource, "apiUrl", assistant.api_url)),
         fastgpt_api_key=_secret(agent_resource, "apiKey", assistant.api_key),
         fastgpt_app_id=str(_value(agent_resource, "appId", assistant.app_id)),