修复：P0+P1 生产稳定性和性能优化（6项）

P0 稳定性修复：
- 告警去重字典添加惰性清理机制，防止长时间运行内存溢出
- Redis 连接断开时显式 close() 后再置 None，防止文件描述符泄漏
- 截图消息 ACK 移至成功路径，失败消息留在 pending list 自动重试

P1 性能优化：
- GPU NMS 添加 torch.no_grad() + 显式释放临时张量，减少显存碎片
- 截图存储改为 Redis 原始 bytes，去掉 Base64 编解码开销（兼容旧格式）
- ROI 配置查询 N+1 改为 get_all_bindings() 单次 JOIN 查询

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

core/alarm_upload_worker.py

@@ -47,6 +47,7 @@ class AlarmUploadWorker:
         self._logger = logging.getLogger("alarm_upload_worker")
 
         self._redis: Optional[redis.Redis] = None
+        self._redis_binary: Optional[redis.Redis] = None  # 用于读取截图 bytes
         self._cos_client = None  # 懒初始化
 
         self._thread: Optional[threading.Thread] = None
@@ -80,6 +81,16 @@ class AlarmUploadWorker:
             )
             self._redis.ping()
             self._logger.info(f"Worker Redis 连接成功: {redis_cfg.host}:{redis_cfg.port}/{redis_cfg.db}")
+
+            # 二进制 Redis 连接（用于读取截图 bytes，不做 decode）
+            self._redis_binary = redis.Redis(
+                host=redis_cfg.host,
+                port=redis_cfg.port,
+                db=redis_cfg.db,
+                password=redis_cfg.password,
+                decode_responses=False,
+                socket_connect_timeout=5,
+            )
         except Exception as e:
             self._logger.error(f"Worker Redis 连接失败: {e}")
             return
@@ -136,6 +147,12 @@ class AlarmUploadWorker:
             except Exception:
                 pass
 
+        if self._redis_binary:
+            try:
+                self._redis_binary.close()
+            except Exception:
+                pass
+
         self._logger.info("AlarmUploadWorker 已停止")
 
     def _worker_loop(self):
@@ -184,21 +201,43 @@ class AlarmUploadWorker:
 
         self._logger.info(f"开始处理告警: {alarm_id} (retry={retry_count})")
 
-        # Step 1: 上传截图到 COS（从 base64 解码后直接上传字节流）
+        # Step 1: 上传截图到 COS
+        snapshot_key = (alarm_data.get("ext_data") or {}).get("_snapshot_key")
         snapshot_b64 = alarm_data.get("snapshot_b64")
         object_key = None
 
-        if snapshot_b64:
+        if snapshot_key:
+            # 新格式：从独立 Redis key 获取原始 bytes
+            try:
+                image_bytes = self._redis_binary.get(snapshot_key) if self._redis_binary else None
+                if image_bytes is None:
+                    self._logger.warning(f"截图 key 已过期: {snapshot_key}, 无截图继续上报")
+                else:
+                    object_key = self._upload_snapshot_to_cos(
+                        image_bytes, alarm_id, alarm_data.get("device_id", "unknown")
+                    )
+                    if object_key is None:
+                        self._handle_retry(alarm_json, "COS 上传失败")
+                        return
+                    # 上传成功后删除临时 key
+                    try:
+                        if self._redis_binary:
+                            self._redis_binary.delete(snapshot_key)
+                    except Exception:
+                        pass
+            except Exception as e:
+                self._logger.error(f"截图获取/上传失败: {e}")
+                self._handle_retry(alarm_json, f"截图处理失败: {e}")
+                return
+        elif snapshot_b64:
+            # 兼容旧格式 (Base64)
             try:
                 import base64
                 image_bytes = base64.b64decode(snapshot_b64)
                 object_key = self._upload_snapshot_to_cos(
-                    image_bytes,
-                    alarm_id,
-                    alarm_data.get("device_id", "unknown"),
+                    image_bytes, alarm_id, alarm_data.get("device_id", "unknown")
                 )
                 if object_key is None:
-                    # COS 上传失败，进入重试
                     self._handle_retry(alarm_json, "COS 上传失败")
                     return
             except Exception as e: