perf(queue): 限制大媒体任务内存并消除准入惊群

将同步与异步非文本任务的准入唤醒改为按任务和全局队首推进，批量续租等待者，避免大量请求同时争抢 advisory lock 和数据库连接。

对 Base64 请求解析、素材解码、上游媒体执行和结果物化增加分层并发限制，复用请求素材并释放重复 Gemini wire 数据；生产 API 默认入口解析并发 16，媒体物化并发 8。

新增 1000 个同步 Gemini 图像编辑请求的模拟上游压力验收，10 MiB 输入和输出下全部成功，Heap 峰值增长约 2.58 GiB，并验证共享上传哈希、单次 attempt 与本地零落盘。

验证：go test ./... -count=1；go vet ./...；gofmt -l 无输出；kubectl kustomize deploy/kubernetes/production；10 MiB Gemini Base64 千任务压力测试通过。

apps/api/internal/runner/upload_test.go

@@ -53,6 +53,60 @@ func TestGeneratedAssetDecisionUploadsInlineImageBase64(t *testing.T) {
 	}
 }
 
+func TestMediaResultMaterializationConcurrencyIsBounded(t *testing.T) {
+	service := New(config.Config{MediaMaterializationConcurrency: 1}, nil, nil)
+	result := map[string]any{
+		"data": []any{map[string]any{
+			"b64_json":  base64.StdEncoding.EncodeToString([]byte("inline image")),
+			"mime_type": "image/png",
+		}},
+	}
+	release, err := service.acquireMediaResultSlot(context.Background(), result)
+	if err != nil {
+		t.Fatalf("acquire first media result slot: %v", err)
+	}
+
+	waitCtx, cancel := context.WithTimeout(context.Background(), 25*time.Millisecond)
+	defer cancel()
+	if _, err := service.acquireMediaResultSlot(waitCtx, result); err == nil {
+		t.Fatal("second media result materialization bypassed configured concurrency")
+	}
+	release()
+
+	release, err = service.acquireMediaResultSlot(context.Background(), result)
+	if err != nil {
+		t.Fatalf("acquire released media result slot: %v", err)
+	}
+	release()
+}
+
+func TestMediaTaskPreacquiresMaterializationSlotForInlineResultTypes(t *testing.T) {
+	t.Parallel()
+	for _, modelType := range []string{
+		"image_generate",
+		"image_edit",
+		"audio_generate",
+		"text_to_speech",
+		"voice_clone",
+		"omni",
+	} {
+		if !mediaTaskNeedsPreUpstreamMaterializationSlot(modelType) {
+			t.Fatalf("%s should preacquire the media materialization slot", modelType)
+		}
+	}
+	for _, modelType := range []string{
+		"text_generate",
+		"text_embedding",
+		"text_rerank",
+		"video_generate",
+		"image_to_video",
+	} {
+		if mediaTaskNeedsPreUpstreamMaterializationSlot(modelType) {
+			t.Fatalf("%s should not hold a media materialization slot across the upstream call", modelType)
+		}
+	}
+}
+
 func TestGeneratedAssetDecisionUploadsVectorDocumentWithoutChangingType(t *testing.T) {
 	item := map[string]any{
 		"type":      "file",