[Hardening] F-14: Fail to Ensure Request Limits and/or Throttling by Default.

### The required feature described as a wish

**Description:** By Default, CloudStack does not enforce rate limiting or request throttling on its API endpoints. Any client with network access to the management plane can issue an unlimited number of API requests without restriction, delay, or penalty.

**Affected Components:** Management API

**Impact:** An attacker or malfunctioning client can flood the API with requests, exhausting server-side resources (e.g., DB) and causing a denial of service. The absence of throttling also enables unlimited automated authentication attempts, which compounds the risk previously described in other reports.

**Steps to Reproduce:**
- Using a custom script or a fuzzing tool, send a high volume of requests in rapid succession to any API endpoint.
- Observe that all requests are processed without any throttling, queuing delay, or rejection based on request rate.

**Recommended Remediation:** Adopt rate-limiting and throttling out-of-the-box. Return `HTTP 429` with a `Retry-After` header when a threshold is exceeded, as an attempt to slow down legit clients (attackers do not slow!)

从 CloudStack Management API 开始，通过向 API 端点发送大量请求来复现该问题。完成标准是默认启用请求限制和节流，过量请求会被延迟或以 HTTP 429 拒绝，并且被拒绝的响应包含 Retry-After 标头。

由索引模型根据 Issue 内容生成。