Redirect bare "/" to the /web UI

The root URI had no content of its own and only showed a pointer
message; send visitors straight to the front-end instead.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

TODO.md

@@ -26,7 +26,7 @@
 
 ## Frontend
 
-- [ ] When the user goes to the / URI in a production server redirect him to /web
+- [x] When the user goes to the / URI in a production server redirect him to /web
 - [ ] Add a link to the API docs (/api/docs) in the navigation (new window - only visible in wide)
 
 ## Improve engine

backend/src/web_server.rs

@@ -168,10 +168,8 @@ pub async fn serve() -> Result<(), Box<dyn Error>> {
         )
         .route_layer(axum::middleware::from_fn(auth))
         .layer(ServiceBuilder::new().layer(cors_layer))
-        .route(
-            "/",
-            get(|| async { "Go to /web for the UI or to /api/docs for the API explorer." }),
-        )
+        // Send visitors straight to the UI; the bare "/" has no content of its own.
+        .route("/", get(|| async { Redirect::temporary("/web") }))
         // The API explorer lives at /api/docs; redirect the bare /api for convenience.
         .route("/api", get(|| async { Redirect::temporary("/api/docs") }))
         .nest_service("/web", static_files)