feat: create structure for the project and first problem

app/main.py

@@ -0,0 +1,9 @@
+from fastapi import FastAPI
+
+from app.routers import api_router
+
+
+def create_app() -> FastAPI:
+    app = FastAPI(title="Math Problems Structure")
+    app.include_router(api_router)
+    return app