袁聪的第二次提交，项目已完整

app/infrastructure/memory_cache.py

@@ -31,3 +31,21 @@ class MemoryCacheAdapter:
             return True
         except Exception:
             return False
+
+    async def delete(self, *keys: str) -> int:
+        """删除若干缓存键；客户端不支持删除时返回 0，缓存只是可重建的优化层。
+
+        记忆热缓存按客户维度失效，失效失败不得阻塞主流程，因此这里吞掉异常，
+        由调用方通过返回值与 `degraded` 语义决定是否告警。
+        """
+        targets = [key for key in keys if key]
+        if not targets:
+            return 0
+        delete = getattr(self.client, "delete", None)
+        if delete is None:
+            return 0
+        try:
+            removed = await delete(*targets)
+        except Exception:
+            return 0
+        return int(removed) if isinstance(removed, int) else len(targets)