init backend, fix frontend module (#307)

backend/main.py

@@ -0,0 +1,17 @@
+from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
+
+app = FastAPI()
+
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+
+@app.get("/data")
+async def read_data() -> dict[str, str]:
+    return {"data": "Hello, World!"}