Prepare for an eventual frontend

Move the backend code into a backend/ directory, and create a frontend/
directory containing an empty sveltekit project.

src/main.rs

@@ -1,50 +0,0 @@
-use async_graphql::http::GraphiQLSource;
-use async_graphql_axum::{GraphQLRequest, GraphQLResponse};
-use axum::{
-    Router,
-    response::Html,
-    routing::{get, post},
-};
-use std::net::SocketAddr;
-
-mod models;
-mod resolvers;
-mod schema;
-
-#[tokio::main]
-async fn main() -> anyhow::Result<()> {
-    let schema = schema::build_schema().await?;
-
-    let app = Router::new()
-        .route(
-            "/graphql",
-            post({
-                let schema = schema.clone();
-                move |req: GraphQLRequest| async move {
-                    GraphQLResponse::from(schema.execute(req.into_inner()).await)
-                }
-            }),
-        )
-        .route(
-            "/graphql",
-            get({
-                let schema = schema.clone();
-                move || async move { axum::Json(schema.sdl()) }
-            }),
-        )
-        .route(
-            "/graphiql",
-            get(Html(GraphiQLSource::build().endpoint("/graphql").finish())),
-        );
-
-    let addr = SocketAddr::from(([0, 0, 0, 0], 3000));
-    println!("listening on http://{}", addr);
-
-    axum::serve(
-        tokio::net::TcpListener::bind(addr).await.unwrap(),
-        app.into_make_service(),
-    )
-    .await
-    .unwrap();
-    Ok(())
-}