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/clients/clients_test.go

@@ -2435,6 +2435,8 @@ func TestVolcesVideoBodyAllowsOnlyTaskPayloadFields(t *testing.T) {
 			"tools":                 []any{map[string]any{"type": "web_search"}},
 			"task_id":               "local-task-id",
 			"runMode":               "simulation",
+			"modelType":             "omni_video",
+			"model_type":            "omni_video",
 			"fps":                   24,
 			"content": []any{
 				map[string]any{"type": "text", "text": "Use <<<element_1>>> in a product reveal"},

apps/api/internal/clients/volces.go

@@ -418,6 +418,8 @@ func cleanProviderBody(body map[string]any) map[string]any {
 		"platformId",
 		"platform_model_id",
 		"platformModelId",
+		"modelType",
+		"model_type",
 	} {
 		delete(out, key)
 	}