fix：修复API状态码和限流配置问题

- 修复登录控制器HTTP状态码问题，现在根据业务结果返回正确状态码
- 调整注册接口限流配置，从3次/5分钟放宽至10次/5分钟（开发环境）
- 新增清除限流记录的调试接口，便于开发测试
- 更新API文档，反映状态码修复和限流调整
- 添加测试脚本验证修复效果

主要修复：
- 业务失败时返回400/401而非200/201状态码
- 注册、登录、GitHub OAuth等接口现在正确处理错误状态码
- 限流配置更适合开发环境测试需求

test-throttle.ps1

@@ -0,0 +1,29 @@
+# Test throttle functionality
+$baseUrl = "http://localhost:3000"
+
+Write-Host "Testing throttle functionality..." -ForegroundColor Green
+
+# Test: Try to register (should work now with increased limit)
+Write-Host "`nTesting register with increased throttle limit..." -ForegroundColor Yellow
+$registerData = @{
+    username = "testuser_throttle"
+    password = "password123"
+    nickname = "Test User Throttle"
+} | ConvertTo-Json
+
+try {
+    $response = Invoke-RestMethod -Uri "$baseUrl/auth/register" -Method POST -Body $registerData -ContentType "application/json" -ErrorAction Stop
+    Write-Host "Status: Success (201)" -ForegroundColor Green
+    Write-Host "Response: $($response.message)" -ForegroundColor Green
+} catch {
+    $statusCode = $_.Exception.Response.StatusCode.value__
+    Write-Host "Status Code: $statusCode" -ForegroundColor $(if ($statusCode -eq 429) { "Yellow" } else { "Red" })
+    
+    if ($_.Exception.Response) {
+        $reader = New-Object System.IO.StreamReader($_.Exception.Response.GetResponseStream())
+        $responseBody = $reader.ReadToEnd()
+        Write-Host "Response: $responseBody" -ForegroundColor Gray
+    }
+}
+
+Write-Host "`nTest completed!" -ForegroundColor Green