refactor(edge): 截图不再保存本地，直接编码为base64上传COS

- ResultReporter: 截图通过 cv2.imencode 编码为 JPEG base64，
  直接放入 Redis 消息，不再调用 ImageStorageManager 保存本地文件
- AlarmUploadWorker: 从 Redis 读取 base64 解码为字节流，
  使用 put_object(Body=bytes) 直接上传 COS，移除 local: 回退逻辑
- 移除 AlarmInfo.snapshot_local_path，改为 snapshot_b64
- COS 未配置时返回 None 进入重试（不再静默回退本地路径）

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

core/alarm_upload_worker.py

@@ -15,7 +15,6 @@ Redis Key 设计：
 
 import json
 import logging
-import os
 import threading
 import time
 from datetime import datetime, timezone
@@ -183,21 +182,16 @@ 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
-        snapshot_local_path = alarm_data.get("snapshot_local_path")
+        # Step 1: 上传截图到 COS（从 base64 解码后直接上传字节流）
+        snapshot_b64 = alarm_data.get("snapshot_b64")
         object_key = None
 
-        if snapshot_local_path:
-            # 截图是异步保存的，等待文件写入完成（最多 3 秒）
-            if not os.path.exists(snapshot_local_path):
-                for _ in range(6):
-                    time.sleep(0.5)
-                    if os.path.exists(snapshot_local_path):
-                        break
-
-            if os.path.exists(snapshot_local_path):
+        if snapshot_b64:
+            try:
+                import base64
+                image_bytes = base64.b64decode(snapshot_b64)
                 object_key = self._upload_snapshot_to_cos(
-                    snapshot_local_path,
+                    image_bytes,
                     alarm_id,
                     alarm_data.get("device_id", "unknown"),
                 )
@@ -205,17 +199,12 @@ class AlarmUploadWorker:
                     # COS 上传失败，进入重试
                     self._handle_retry(alarm_json, "COS 上传失败")
                     return
-                elif object_key == "":
-                    # COS 未配置，使用本地截图路径作为回退
-                    captures_base = os.path.join("data", "captures")
-                    rel_path = os.path.relpath(snapshot_local_path, captures_base)
-                    rel_path = rel_path.replace("\\", "/")
-                    object_key = f"local:{rel_path}"
-                    self._logger.info(f"使用本地截图路径: {object_key}")
-            else:
-                self._logger.warning(f"截图文件不存在: {snapshot_local_path}")
+            except Exception as e:
+                self._logger.error(f"截图解码/上传失败: {e}")
+                self._handle_retry(alarm_json, f"截图处理失败: {e}")
+                return
 
-        # Step 2: HTTP 上报告警元数据
+        # Step 2: HTTP 上报告警元数据（不含截图二进制数据）
         report_data = {
             "alarm_id": alarm_data.get("alarm_id"),
             "alarm_type": alarm_data.get("alarm_type"),
@@ -234,14 +223,6 @@ class AlarmUploadWorker:
         if success:
             self._stats["processed"] += 1
             self._logger.info(f"告警上报成功: {alarm_id}")
-
-            # 仅在 COS 上传成功时删除本地截图；本地回退模式(local:)不删除
-            if snapshot_local_path and os.path.exists(snapshot_local_path) and object_key and not object_key.startswith("local:"):
-                try:
-                    os.remove(snapshot_local_path)
-                    self._logger.debug(f"已删除本地截图: {snapshot_local_path}")
-                except Exception as e:
-                    self._logger.warning(f"删除本地截图失败: {e}")
         else:
             # HTTP 上报失败，进入重试
             self._handle_retry(alarm_json, "HTTP 上报失败")
@@ -277,13 +258,13 @@ class AlarmUploadWorker:
             self._logger.warning(f"告警结束上报异常: {e}")
 
     def _upload_snapshot_to_cos(
-        self, local_path: str, alarm_id: str, device_id: str
+        self, image_bytes: bytes, alarm_id: str, device_id: str
     ) -> Optional[str]:
         """
-        上传截图到腾讯云 COS
+        上传截图到腾讯云 COS（直接从内存字节流上传）
 
         Args:
-            local_path: 本地截图路径
+            image_bytes: JPEG 图片字节
             alarm_id: 告警ID
             device_id: 设备ID
 
@@ -292,8 +273,8 @@ class AlarmUploadWorker:
         """
         cos_cfg = self._settings.cos
         if not cos_cfg.secret_id or not cos_cfg.bucket:
-            self._logger.warning("COS 未配置，跳过截图上传")
-            return ""
+            self._logger.error("COS 未配置（缺少 secret_id 或 bucket），无法上传截图")
+            return None
 
         # 懒初始化 COS 客户端
         if self._cos_client is None:
@@ -317,10 +298,11 @@ class AlarmUploadWorker:
         object_key = f"alarms/{device_id}/{date_str}/{alarm_id}.jpg"
 
         try:
-            self._cos_client.put_object_from_local_file(
+            self._cos_client.put_object(
                 Bucket=cos_cfg.bucket,
-                LocalFilePath=local_path,
+                Body=image_bytes,
                 Key=object_key,
+                ContentType="image/jpeg",
             )
             self._stats["cos_uploaded"] += 1
             self._logger.info(f"COS 上传成功: {object_key}")