dev/e2e: disposable server for app e2e / agent UI testing

`dev/e2e/e2e.sh up` runs an isolated ImageApi (port 8090, own build dir,
db, thumbnails, HLS) next to a real local server, serving a copy of a
synthetic fixture library. Every fixture image has its path, date and
scenario burned into the pixels; manifest.json records expected dates,
GPS, cameras, tags and counts. `reset` restores the baseline.

- LOCAL_BIND_URL makes the hardcoded localhost:8088 listener
  configurable (default unchanged; empty disables it) so a second
  instance can start.
- create_user bin: the server has no registration route; idempotent.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/main.rs

@@ -285,7 +285,7 @@ fn main() -> std::io::Result<()> {
         // Spawn the on-disk reel-cache sweeper (bounds pre-gen + on-demand reels).
         reels::spawn_reel_cache_sweeper(app_state.clone()).await;
 
-        HttpServer::new(move || {
+        let server = HttpServer::new(move || {
             let user_dao = SqliteUserDao::new();
             let favorites_dao = SqliteFavoriteDao::new();
             let tag_dao = SqliteTagDao::default();
@@ -471,10 +471,20 @@ fn main() -> std::io::Result<()> {
                 .app_data::<Data<InsightGenerator>>(Data::new(app_data.insight_generator.clone()))
                 .wrap(prometheus.clone())
         })
-        .bind(dotenv::var("BIND_URL").unwrap())?
-        .bind("localhost:8088")?
-        .run()
-        .await
+        .bind(dotenv::var("BIND_URL").unwrap())?;
+
+        // Secondary loopback listener. Defaults to localhost:8088; set
+        // LOCAL_BIND_URL to move it, or to an empty string to skip it —
+        // required to run a second instance (e.g. the dev/e2e harness)
+        // alongside one that already owns 8088.
+        let local_bind = env::var("LOCAL_BIND_URL").unwrap_or_else(|_| "localhost:8088".into());
+        let server = if local_bind.trim().is_empty() {
+            server
+        } else {
+            server.bind(local_bind.trim())?
+        };
+
+        server.run().await
     })
 }