perf(types): add Union type declaration for workflow nodes

- Introduce a `Nodes` type as a Union of all workflow node classes.
- Improves type checking and IDE autocompletion.

api/app/core/workflow/nodes/enums.py

@@ -1,4 +1,14 @@
 from enum import StrEnum
+from typing import Union
+
+from app.core.workflow.nodes.base_node import BaseNode
+from app.core.workflow.nodes.if_else import IfElseNode
+from app.core.workflow.nodes.llm import LLMNode
+from app.core.workflow.nodes.agent import AgentNode
+from app.core.workflow.nodes.transform import TransformNode
+from app.core.workflow.nodes.start import StartNode
+from app.core.workflow.nodes.end import EndNode
+
 
 class NodeType(StrEnum):
     START = "start"
@@ -13,3 +23,14 @@ class NodeType(StrEnum):
     HTTP_REQUEST = "http-request"
     TOOL = "tool"
     AGENT = "agent"
+
+
+WorkflowNode = Union[
+    BaseNode,
+    StartNode,
+    EndNode,
+    LLMNode,
+    IfElseNode,
+    AgentNode,
+    TransformNode,
+]

api/app/core/workflow/nodes/node_factory.py

@@ -8,7 +8,8 @@ import logging
 from typing import Any
 
 from app.core.workflow.nodes.base_node import BaseNode
-from app.core.workflow.nodes.enums import NodeType
+from app.core.workflow.nodes.enums import NodeType, WorkflowNode
+from app.core.workflow.nodes.if_else import IfElseNode
 from app.core.workflow.nodes.llm import LLMNode
 from app.core.workflow.nodes.agent import AgentNode
 from app.core.workflow.nodes.transform import TransformNode
@@ -25,16 +26,17 @@ class NodeFactory:
     """
 
     # 节点类型注册表
-    _node_types: dict[str, type[BaseNode]] = {
+    _node_types: dict[str, type[WorkflowNode]] = {
         NodeType.START: StartNode,
         NodeType.END: EndNode,
         NodeType.LLM: LLMNode,
         NodeType.AGENT: AgentNode,
         NodeType.TRANSFORM: TransformNode,
+        NodeType.IF_ELSE: IfElseNode
     }
 
     @classmethod
-    def register_node_type(cls, node_type: str, node_class: type[BaseNode]):
+    def register_node_type(cls, node_type: str, node_class: type[WorkflowNode]):
         """注册新的节点类型
 
         Args:
@@ -55,7 +57,7 @@ class NodeFactory:
         cls,
         node_config: dict[str, Any],
         workflow_config: dict[str, Any]
-    ) -> BaseNode | None:
+    ) -> WorkflowNode | None:
         """创建节点实例
 
         Args: