refactor(backend): use async fn syntax per clippy lint

backend/src/web/mw_auth.rs

@@ -39,11 +39,10 @@ pub async fn mw_ctx_resolver(
 impl<S: Send + Sync> FromRequestParts<S> for Ctx {
     type Rejection = LoftError;
 
-    fn from_request_parts(
+    async fn from_request_parts(
         parts: &mut axum::http::request::Parts,
         _: &S,
-    ) -> impl Future<Output = Result<Self, Self::Rejection>> + Send {
-        async move {
+    ) -> Result<Self, Self::Rejection> {
         parts
             .extensions
             .get::<Result<Ctx, LoftError>>()
@@ -51,4 +50,3 @@ impl<S: Send + Sync> FromRequestParts<S> for Ctx {
             .clone()
     }
 }
-}