fix: reject duplicate param names in route registration

[Lcos-000]

What type of PR is this?

fix

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fix: 路由注册时拒绝重复参数名

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en:
When a route contains duplicate parameter names in different path segments, such as /user/:id/order/:id, Params.ByName("id") always returns the first matched value. As a result, the later parameter value cannot be retrieved, which may lead to subtle and hard-to-debug issues.

This PR adds checkDuplicateParams to detect and reject such routes during registration, with a clear panic message. This makes invalid route definitions fail fast instead of causing unexpected runtime behavior.

zh:
当路由在不同路径段中包含重复参数名时，例如 /user/:id/order/:id，Params.ByName("id") 始终只会返回第一个匹配到的值，后续同名参数的值无法获取。这可能导致隐蔽且难以排查的问题。

本 PR 新增 checkDuplicateParams，在路由注册阶段检测并拒绝此类路由，并给出明确的 panic 信息。这样可以让非法路由定义尽早失败，避免运行时出现非预期行为。

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