Add workflow editor and node types support in frontend and backend

- Introduce a new workflow editor component for visualizing and managing workflows, allowing users to add nodes and define connections.
- Implement backend support for node types, including validation and constraints for workflow graphs.
- Add new API endpoints for retrieving node types and their specifications.
- Enhance the AssistantPage to integrate the workflow editor, enabling users to create and edit workflows directly.
- Update frontend components to support new workflow functionalities, including condition edges and generic nodes.
- Refactor existing code to accommodate the new workflow features and improve overall structure.

backend/routes/assistants.py

@@ -7,6 +7,7 @@ from db.session import get_session
 from fastapi import APIRouter, Depends, HTTPException
 from schemas import AssistantOut, AssistantUpsert
 from services.masking import mask, resolve_incoming_key
+from services.node_specs import validate_graph
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
@@ -14,6 +15,15 @@ router = APIRouter(prefix="/api/assistants", tags=["assistants"])
 CAPABILITIES = ("LLM", "ASR", "TTS", "Realtime", "Embedding")
 
 
+def _validate_workflow(body: AssistantUpsert) -> None:
+    """workflow 类型:保存前校验图结构,不通过则 400。其他类型跳过。"""
+    if body.type != "workflow":
+        return
+    errors = validate_graph(body.graph or {})
+    if errors:
+        raise HTTPException(400, "工作流校验失败:" + ";".join(errors))
+
+
 async def _sync_bindings(
     session: AsyncSession, assistant_id: str, resource_ids: dict[str, str]
 ) -> None:
@@ -82,6 +92,7 @@ async def list_assistants(session: AsyncSession = Depends(get_session)):
 async def create_assistant(
     body: AssistantUpsert, session: AsyncSession = Depends(get_session)
 ):
+    _validate_workflow(body)
     data = body.model_dump()
     resource_ids = data.pop("model_resource_ids")
     assistant = Assistant(id=f"asst_{uuid.uuid4().hex[:12]}", **data)
@@ -141,6 +152,7 @@ async def update_assistant(
     assistant = await session.get(Assistant, assistant_id)
     if not assistant:
         raise HTTPException(404, "助手不存在")
+    _validate_workflow(body)
     data = body.model_dump()
     resource_ids = data.pop("model_resource_ids")
     data["api_key"] = resolve_incoming_key(data["api_key"], assistant.api_key)

backend/routes/node_types.py

@@ -0,0 +1,14 @@
+"""工作流节点类型目录。前端画布据此渲染「添加节点」面板与节点编辑表单。
+
+规格是只读的、与代码同生命周期(改了要重启后端 + 前端刷新),所以无需鉴权与缓存层。
+"""
+
+from fastapi import APIRouter
+from services.node_specs import node_types_response
+
+router = APIRouter(prefix="/api/node-types", tags=["workflow"])
+
+
+@router.get("")
+async def list_node_types():
+    return node_types_response()