Add Redis-based one-time download token support

Integrate Redis as a backend for one-time download token validation, with in-memory fallback. Added RedisManager for connection lifecycle, TokenStore for atomic token usage checks, and related configuration via environment variables. Updated download flow to ensure tokens are single-use, and improved API robustness for batch operations. Updated dependencies to include redis and cachetools.

service/redis/__init__.py

@@ -0,0 +1,88 @@
+"""
+Redis 服务模块
+
+提供 Redis 异步客户端的生命周期管理。
+通过环境变量配置连接参数，未配置时不初始化客户端。
+"""
+from typing import ClassVar
+
+import redis.asyncio as aioredis
+from loguru import logger as l
+
+from utils.conf import appmeta
+
+
+class RedisManager:
+    """
+    Redis 连接管理器
+
+    使用 ClassVar 管理全局单例客户端。
+    """
+
+    _client: ClassVar[aioredis.Redis | None] = None
+    """Redis 客户端实例"""
+
+    _is_available: ClassVar[bool] = False
+    """Redis 是否可用"""
+
+    @classmethod
+    def is_configured(cls) -> bool:
+        """检查是否配置了 Redis"""
+        return appmeta.redis_url is not None
+
+    @classmethod
+    def is_available(cls) -> bool:
+        """检查 Redis 是否可用"""
+        return cls._is_available
+
+    @classmethod
+    def get_client(cls) -> aioredis.Redis | None:
+        """
+        获取 Redis 客户端实例。
+
+        :return: Redis 客户端，未配置或连接失败时返回 None
+        """
+        return cls._client if cls._is_available else None
+
+    @classmethod
+    async def connect(cls) -> None:
+        """
+        连接 Redis 服务器。
+
+        在应用启动时调用，如果未配置 Redis 则跳过。
+        """
+        if not cls.is_configured():
+            l.info("未配置 REDIS_URL，跳过 Redis 连接")
+            return
+
+        try:
+            cls._client = aioredis.Redis(
+                host=appmeta.redis_url,
+                port=appmeta.redis_port,
+                password=appmeta.redis_password,
+                db=appmeta.redis_db,
+                protocol=appmeta.redis_protocol,
+            )
+
+            # 测试连接
+            await cls._client.ping()
+            cls._is_available = True
+            l.info(f"Redis 连接成功: {appmeta.redis_url}:{appmeta.redis_port}")
+
+        except Exception as e:
+            l.warning(f"Redis 连接失败，将使用内存缓存作为降级方案: {e}")
+            cls._client = None
+            cls._is_available = False
+
+    @classmethod
+    async def disconnect(cls) -> None:
+        """
+        断开 Redis 连接。
+
+        在应用关闭时调用。
+        """
+        if cls._client is not None:
+            await cls._client.close()
+            cls._client = None
+            cls._is_available = False
+            l.info("Redis 连接已关闭")