perf(api-server): tune gallery load shedding

server-rs/crates/api-server/src/app.rs

@@ -1,7 +1,7 @@
 use axum::{
     Router,
     body::Body,
-    extract::Extension,
+    extract::{Extension, FromRef},
     http::Request,
     middleware,
     response::Response,
@@ -22,7 +22,7 @@ use crate::{
     request_context::{RequestContext, attach_request_context, resolve_request_id},
     response_headers::propagate_request_id_header,
     runtime_inventory::get_runtime_inventory_state,
-    state::AppState,
+    state::{AppState, BackpressureState},
     telemetry::record_http_observability,
     tracking::record_route_tracking_event_after_success,
     vector_engine_audio_generation::{
@@ -79,7 +79,7 @@ pub fn build_router(state: AppState) -> Router {
         ))
         // HTTP 背压在业务路由外侧快拒绝，避免过载请求继续占用 SpacetimeDB facade 与业务执行资源。
         .layer(middleware::from_fn_with_state(
-            state.clone(),
+            BackpressureState::from_ref(&state),
             limit_concurrent_requests,
         ))
         // 错误归一化层放在 tracing 里侧，让 tracing 记录到最终对外返回的状态与错误体形态。