配置 API Key 环境变量，完成 FastAPI 基础配置

backend/app/main.py

@@ -0,0 +1,19 @@
+from fastapi import FastAPI
+from config import settings
+
+app = FastAPI(
+    title=settings.APP_NAME,
+    openapi_url=f"{settings.API_V1_STR}/openapi.json"
+)
+
+@app.get("/")
+async def root():
+    return {
+        "message": f"Welcome to {settings.APP_NAME}",
+        "status": "online",
+        "debug_mode": settings.DEBUG
+    }
+
+if __name__ == "__main__":
+    import uvicorn
+    uvicorn.run("main:app", host="127.0.0.1", port=8000, reload=True)