fix: auto-fix code issues (cron)

- 修复重复导入/字段
- 修复异常处理
- 修复PEP8格式问题
- 添加类型注解

backend/rate_limiter.py

@@ -5,11 +5,11 @@ API 限流中间件
 支持基于内存的滑动窗口限流
 """
 
-import time
 import asyncio
-from typing import Dict, Optional, Callable
-from dataclasses import dataclass
+import time
 from collections import defaultdict
+from collections.abc import Callable
+from dataclasses import dataclass
 from functools import wraps
 
 
@@ -37,7 +37,7 @@ class SlidingWindowCounter:
 
     def __init__(self, window_size: int = 60):
         self.window_size = window_size
-        self.requests: Dict[int, int] = defaultdict(int)  # 秒级计数
+        self.requests: dict[int, int] = defaultdict(int)  # 秒级计数
         self._lock = asyncio.Lock()
         self._cleanup_lock = asyncio.Lock()
 
@@ -69,13 +69,13 @@ class RateLimiter:
 
     def __init__(self):
         # key -> SlidingWindowCounter
-        self.counters: Dict[str, SlidingWindowCounter] = {}
+        self.counters: dict[str, SlidingWindowCounter] = {}
         # key -> RateLimitConfig
-        self.configs: Dict[str, RateLimitConfig] = {}
+        self.configs: dict[str, RateLimitConfig] = {}
         self._lock = asyncio.Lock()
         self._cleanup_lock = asyncio.Lock()
 
-    async def is_allowed(self, key: str, config: Optional[RateLimitConfig] = None) -> RateLimitInfo:
+    async def is_allowed(self, key: str, config: RateLimitConfig | None = None) -> RateLimitInfo:
         """
         检查是否允许请求
 
@@ -143,7 +143,7 @@ class RateLimiter:
             retry_after=max(0, config.window_size) if current_count >= config.requests_per_minute else 0,
         )
 
-    def reset(self, key: Optional[str] = None):
+    def reset(self, key: str | None = None):
         """重置限流计数器"""
         if key:
             self.counters.pop(key, None)
@@ -154,7 +154,7 @@ class RateLimiter:
 
 
 # 全局限流器实例
-_rate_limiter: Optional[RateLimiter] = None
+_rate_limiter: RateLimiter | None = None
 
 
 def get_rate_limiter() -> RateLimiter:
@@ -166,7 +166,7 @@ def get_rate_limiter() -> RateLimiter:
 
 
 # 限流装饰器（用于函数级别限流）
-def rate_limit(requests_per_minute: int = 60, key_func: Optional[Callable] = None):
+def rate_limit(requests_per_minute: int = 60, key_func: Callable | None = None):
     """
     限流装饰器