feat(acceptance): 增加生产同构媒体压力验收模式

引入动态流量门禁、隔离验收身份与协议级 Gemini/Volces 模拟器，覆盖双站点 API、Worker、PostgreSQL、River、账务、回调和媒体物化链路。

新增 P24/P28/P32 容量阶梯、Worker 强杀恢复、真实小流量 canary、CAS 放量和失败保持 validation 的生产编排；Worker 执行槽、连接池、媒体并发和双站点副本数改为环境配置。

验证：Go 全量测试、真实 PostgreSQL 迁移集成测试、迁移安全检查、OpenAPI 生成、ShellCheck、Kustomize、gofmt 和 git diff --check。

apps/api/internal/httpapi/handlers.go

@@ -1095,6 +1095,11 @@ func (s *Server) createTask(kind string, compatible bool) http.Handler {
 			writeTaskError(http.StatusUnauthorized, "unauthorized", nil)
 			return
 		}
+		admission, err := s.authorizeTaskTraffic(r, user)
+		if err != nil {
+			writeTaskTrafficError(w, err, targetProtocol)
+			return
+		}
 
 		body, err := s.decodeTaskRequestBody(r.Context(), w, r, kind)
 		if err != nil {
@@ -1147,10 +1152,16 @@ func (s *Server) createTask(kind string, compatible bool) http.Handler {
 			return
 		}
 
+		runMode, err := s.admittedTaskRunMode(admission, prepared.Body)
+		if err != nil {
+			writeTaskTrafficError(w, err, targetProtocol)
+			return
+		}
 		createInput := store.CreateTaskInput{
 			Kind:            kind,
 			Model:           model,
-			RunMode:         runModeFromRequest(prepared.Body),
+			RunMode:         runMode,
+			AcceptanceRunID: admission.AcceptanceRunID,
 			Async:           responsePlan.asyncMode,
 			Request:         prepared.Body,
 			ConversationID:  prepared.ConversationID,