feat: serve derivative files via GET /assets/{id}/derivatives/{profile}

- ReadDerivativeHandler queries DerivativeRepository + FileStoragePort
- Profile URL param: thumbnail, thumbnail_large, web_optimized, video_sd
- Immutable cache headers (derivatives don't change once generated)
- Wired into bootstrap catalog service builder

crates/presentation/src/routes.rs

@@ -29,6 +29,10 @@ pub fn api_v1_router() -> Router<AppState> {
         .route("/assets/{id}", get(assets::get_asset))
         .route("/assets/{id}/metadata", put(assets::update_metadata))
         .route("/assets/{id}/file", get(assets::serve_file))
+        .route(
+            "/assets/{id}/derivatives/{profile}",
+            get(assets::serve_derivative),
+        )
         .route("/assets/{id}/tags", post(assets::tag_asset))
         // sharing
         .route("/sharing", post(sharing::share_resource))