修复：截图处理器 Redis 断线后无法自动重连的死循环

- 重连失败时不再置 cloud_redis=None，避免后续循环走错分支
- except Exception 分支增加 cloud_redis is None 判断，主动触发重连
- 重连成功后重置退避计时器

core/screenshot_handler.py

@@ -127,12 +127,12 @@ class ScreenshotHandler:
 
     # ==================== 重连 ====================
 
-    def _reconnect_cloud_redis(self):
-        """重建云端 Redis 连接"""
+    def _reconnect_cloud_redis(self) -> bool:
+        """重建云端 Redis 连接，返回是否成功"""
         try:
             from core.config_sync import _build_keepalive_options
             cfg = self._settings.cloud_redis
-            self._cloud_redis = redis.Redis(
+            new_client = redis.Redis(
                 host=cfg.host,
                 port=cfg.port,
                 db=cfg.db,
@@ -145,11 +145,14 @@ class ScreenshotHandler:
                 socket_keepalive_options=_build_keepalive_options(),
                 health_check_interval=15,
             )
-            self._cloud_redis.ping()
+            new_client.ping()
+            self._cloud_redis = new_client
             logger.info("[截图] 云端 Redis 重连成功")
+            return True
         except Exception as e:
             logger.warning("[截图] 云端 Redis 重连失败: %s", e)
-            self._cloud_redis = None
+            # 不置 None，避免后续循环永远无法触发 ConnectionError 重连
+            return False
 
     # ==================== 主循环 ====================
 
@@ -196,16 +199,25 @@ class ScreenshotHandler:
                 if self._stop_event.is_set():
                     return
                 logger.warning("[截图] 云端 Redis 连接断开: %s, %ds 后重连...", e, backoff)
-                self._reconnect_cloud_redis()
                 self._stop_event.wait(backoff)
+                self._reconnect_cloud_redis()
                 backoff = min(backoff * 2, max_backoff)
 
             except Exception as e:
                 if self._stop_event.is_set():
                     return
-                logger.warning("[截图] 监听异常: %s, %ds 后重试", e, backoff)
-                self._stop_event.wait(backoff)
-                backoff = min(backoff * 2, max_backoff)
+                # cloud_redis 为 None 时主动重连，避免死循环
+                if self._cloud_redis is None:
+                    logger.warning("[截图] 云端 Redis 未连接, %ds 后重连...", backoff)
+                    self._stop_event.wait(backoff)
+                    if self._reconnect_cloud_redis():
+                        backoff = 5  # 重连成功，重置退避
+                    else:
+                        backoff = min(backoff * 2, max_backoff)
+                else:
+                    logger.warning("[截图] 监听异常: %s, %ds 后重试", e, backoff)
+                    self._stop_event.wait(backoff)
+                    backoff = min(backoff * 2, max_backoff)
 
     # ==================== 请求处理 ====================