feat: implement pipeline execution engine with DAG validation

backend/app/main.py

@@ -1,7 +1,10 @@
 from fastapi import FastAPI
+from app.routes.pipeline import router as pipeline_router
 
 app = FastAPI()
 
 @app.get("/")
 def root():
-    return {"message": "Backend running"}
+    return {"message": "Backend running"}
+
+app.include_router(pipeline_router)

backend/app/pipeline/schemas.py

@@ -0,0 +1,14 @@
+from pydantic import BaseModel
+from typing import List
+
+class Node(BaseModel):
+    id: str
+    type: str
+
+class Edge(BaseModel):
+    source: str
+    target: str
+
+class Pipeline(BaseModel):
+    nodes: List[Node]
+    edges: List[Edge]

backend/app/routes/pipeline.py

@@ -0,0 +1,25 @@
+from fastapi import APIRouter, HTTPException
+from app.pipeline.executor import run_pipeline
+from app.pipeline.schemas import Pipeline
+
+router = APIRouter()
+
+@router.post("/run_pipeline")
+def execute_pipeline(pipeline: Pipeline):
+    try:
+        results = run_pipeline(pipeline.model_dump())
+        return{
+            "status": "success",
+            "results": results
+        }
+    except ValueError as e:
+        raise HTTPException(
+            status_code=400,
+            detail=str(e)
+        )
+
+    except Exception:
+        raise HTTPException(
+            status_code=500,
+            detail="Internal server error"
+        )