feat: render scrobble partial into initial HTML returned (SSR)

This means the scrobble data will show on page load rather than waiting
for a JS fetch.

Dockerfile

···
 WORKDIR /usr/src/myivo-server
 COPY server .
 
+# point to minimised, production versions of build artefacts
+RUN sed -i "s|build/app|build/app.min|g" files/index.html
 RUN cargo install --profile release --locked --path .
 
 # run on different image
···
 
 WORKDIR /root
 
-COPY --from=build-js /usr/src/myivo/index.html ./
-# point to minimised, production versions of build artefacts
-RUN sed -i "s|build/app|build/app.min|g" index.html
 COPY --from=build-js /usr/src/myivo/images ./images 
 COPY --from=build-js /usr/src/myivo/fonts ./fonts
 COPY --from=build-js /usr/src/myivo/build ./build

frontend/esbuild.js

···
         headers: req.headers,
       };
       const route =
-        req.url === "/scrobbles"
+        req.url === "/" || req.url === "/scrobbles"
           ? { hostname: "127.0.0.1", port: 8080 }
           : { hostname: host, port };
       const routedOptions = { ...options, ...route };

frontend/index.html server/files/index.html

···
         />
       </div>
     </div>
-    <div
-      class="scrobble-bar"
-      hx-get="/scrobbles"
-      hx-trigger="load, every 30s"
-    />
+    <div class="scrobble-bar" hx-get="/scrobbles" hx-trigger="every 30s">
+      {{scrobbles}}
+    </div>
   </body>
 </html>

server/src/index.rs

···
+use crate::scrobble_monitor::ScrobbleMonitor;
+
+pub async fn render_index(monitor: &mut ScrobbleMonitor) -> anyhow::Result<String> {
+    let index_template = include_str!("../files/index.html");
+    let scrobble_partial = monitor.get_scrobble().await?;
+
+    Ok(index_template.replace("{{scrobbles}}", &scrobble_partial.into_string()))
+}

server/src/main.rs

···
+mod index;
 mod scrobble;
 mod scrobble_monitor;
 
 use std::{env, net::SocketAddr};
 
+use crate::index::render_index;
 use crate::scrobble_monitor::ScrobbleMonitor;
 
 use axum::{
     http::{HeaderName, HeaderValue, StatusCode},
-    response::IntoResponse,
+    response::{Html, IntoResponse},
     routing::{get, get_service},
     Extension, Router,
 };
···
     let monitor = ScrobbleMonitor::new(env::var("LAST_FM_API_KEY")?);
 
     let app = Router::new()
+        .route("/", get(render_index_handler))
         .route("/scrobbles", get(get_scrobble))
         .fallback(get_service(ServeDir::new(".")))
         .layer(
···
     axum::serve(listener, app).await?;
 
     Ok(())
+}
+
+async fn render_index_handler(
+    Extension(mut monitor): Extension<ScrobbleMonitor>,
+) -> impl IntoResponse {
+    render_index(&mut monitor).await.map(Html).map_err(|err| {
+        tracing::error!("failed to get data from last.fm: {err:?}");
+        StatusCode::BAD_GATEWAY
+    })
 }
 
 async fn get_scrobble(Extension(mut monitor): Extension<ScrobbleMonitor>) -> impl IntoResponse {