P0 实现请求限流中间件：每分钟60次请求限制，保护第三方API配额

AssetManager.API/Middleware/RateLimitMiddleware.cs

@@ -0,0 +1,68 @@
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Caching.Memory;
+using Microsoft.Extensions.Logging;
+using System;
+using System.Threading.Tasks;
+
+namespace AssetManager.API.Middleware;
+
+/// <summary>
+/// 请求限流中间件：限制每个用户的请求频率，保护第三方API配额
+/// </summary>
+public class RateLimitMiddleware
+{
+    private readonly RequestDelegate _next;
+    private readonly IMemoryCache _cache;
+    private readonly ILogger<RateLimitMiddleware> _logger;
+
+    // 限流配置：每个用户每分钟最多请求60次（平均1秒1次，足够正常使用）
+    private const int Limit = 60;
+    private const int WindowSeconds = 60;
+    private const string CacheKeyPrefix = "RateLimit_";
+
+    public RateLimitMiddleware(RequestDelegate next, IMemoryCache cache, ILogger<RateLimitMiddleware> logger)
+    {
+        _next = next;
+        _cache = cache;
+        _logger = logger;
+    }
+
+    public async Task InvokeAsync(HttpContext context)
+    {
+        // 获取用户ID（未登录则用IP地址）
+        var userId = context.User.FindFirst(System.Security.Claims.ClaimTypes.NameIdentifier)?.Value 
+                     ?? context.Connection.RemoteIpAddress?.ToString() 
+                     ?? "anonymous";
+
+        var cacheKey = $"{CacheKeyPrefix}{userId}";
+        
+        // 获取当前窗口的请求计数
+        var requestCount = _cache.Get<int>(cacheKey);
+        
+        if (requestCount >= Limit)
+        {
+            _logger.LogWarning("用户 {UserId} 请求超过限流限制，当前计数: {Count}", userId, requestCount);
+            context.Response.StatusCode = StatusCodes.Status429TooManyRequests;
+            context.Response.ContentType = "application/json";
+            await context.Response.WriteAsync(System.Text.Json.JsonSerializer.Serialize(new
+            {
+                code = 429,
+                message = "请求过于频繁，请稍后再试",
+                data = (object)null
+            }));
+            return;
+        }
+
+        // 计数+1，首次访问设置过期时间
+        if (requestCount == 0)
+        {
+            _cache.Set(cacheKey, 1, TimeSpan.FromSeconds(WindowSeconds));
+        }
+        else
+        {
+            _cache.Set(cacheKey, requestCount + 1, _cache.GetEntry(cacheKey).AbsoluteExpirationRelativeToNow ?? TimeSpan.FromSeconds(WindowSeconds));
+        }
+
+        await _next(context);
+    }
+}

AssetManager.API/Program.cs

@@ -118,6 +118,9 @@ app.Services.InitializeDatabase();
 // 全局异常处理中间件（必须放在最前面）
 app.UseMiddleware<GlobalExceptionMiddleware>();
 
+// 请求限流中间件：限制用户请求频率，保护第三方API配额
+app.UseMiddleware<RateLimitMiddleware>();
+
 if (app.Environment.IsDevelopment())
 {
     app.UseSwagger();