feat(server): Go API Server Phase 0 骨架

[Color2333]

全量重写 Phase 0：绞杀者入口 + 设备码授权移植。

[gitguardian]

⚠️ GitGuardian has uncovered 1 secret following the scan of your pull request.

Please consider investigating the findings and remediating the incidents. Failure to do so may lead to compromising the associated services or software components.

🔎 Detected hardcoded secret in your pull request

GitGuardian id	GitGuardian status	Secret	Commit	Filename
38044907	Triggered	JSON Web Token	65d5408	server/auth_test.go	View secret

🛠 Guidelines to remediate hardcoded secrets

1. Understand the implications of revoking this secret by investigating where it is used in your code.
2. Replace and store your secret safely. Learn here the best practices.
3. Revoke and rotate this secret.
4. If possible, rewrite git history. Rewriting git history is not a trivial act. You might completely break other contributing developers' workflow and you risk accidentally deleting legitimate data.

To avoid such incidents in the future consider

• following these best practices for managing and storing secrets including API keys and other credentials
• install secret detection on pre-commit to catch secret before it leaves your machine and ease remediation.

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^{🦉 GitGuardian detects secrets in your source code to help developers and security teams secure the modern development process. You are seeing this because you or someone else with access to this repository has authorized GitGuardian to scan your pull request.}

[github-actions]

🔍 OpenCode PR Review Required

这是一个受保护的分支，merge 前需要进行 code review。

请运行以下命令进行 OpenCode review：

/oc review https://github.com/Color2333/PaperMind/pull/$PR_NUM

或者在 PR 页面评论 /oc 来触发 OpenCode review。

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This is an automated reminder from PR Review Gate.