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/gemini_compat.go

@@ -117,6 +117,11 @@ func (s *Server) geminiGenerateContent(w http.ResponseWriter, r *http.Request) {
 		writeGeminiTaskError(http.StatusUnauthorized, "unauthorized", nil, "unauthorized")
 		return
 	}
+	admission, err := s.authorizeTaskTraffic(r, user)
+	if err != nil {
+		writeTaskTrafficError(w, err, clients.ProtocolGeminiGenerateContent)
+		return
+	}
 	releaseRequestBody, err := s.acquireMediaRequestBodySlot(r.Context())
 	if err != nil {
 		return
@@ -166,10 +171,16 @@ func (s *Server) geminiGenerateContent(w http.ResponseWriter, r *http.Request) {
 	mapping.Body = nil
 	releaseRequestBody()
 	releaseRequestBody = nil
+	runMode, err := s.admittedTaskRunMode(admission, prepared.Body)
+	if err != nil {
+		writeTaskTrafficError(w, err, clients.ProtocolGeminiGenerateContent)
+		return
+	}
 	createInput := store.CreateTaskInput{
 		Kind:            mapping.Kind,
 		Model:           mapping.Model,
-		RunMode:         runModeFromRequest(prepared.Body),
+		RunMode:         runMode,
+		AcceptanceRunID: admission.AcceptanceRunID,
 		Async:           false,
 		Request:         prepared.Body,
 		ConversationID:  prepared.ConversationID,