fix(core): handle HTTPS core monitor configuration

[Suyunmeng]

Summary / 摘要

• The core monitor now reads OpenList's configured HTTPS port from the active data directory instead of reusing the managed HTTP port.
  核心监控现在从当前数据目录读取 OpenList 配置的 HTTPS 端口，而不是复用 Desktop 管理的 HTTP 端口。

• HTTP monitoring keeps its existing port and configuration synchronization behavior.
  HTTP 监控保留现有端口及配置同步行为。

• Local HTTPS health checks accept self-signed certificates commonly used by local OpenList deployments.
  本地 HTTPS 健康检查允许本地 OpenList 部署通常使用的自签名证书。

• Invalid or unavailable HTTPS configuration is reported as unavailable without constructing an incorrect HTTPS-to-HTTP fallback URL.
  HTTPS 配置无效或不可用时会报告为不可用，不会构造错误的 HTTPS 到 HTTP 回退地址。

• The web management URL now uses the same monitored endpoint and remains empty when no valid HTTPS endpoint is available.
  Web 管理地址现在使用与监控相同的端点，在没有有效 HTTPS 端点时保持为空。

• This PR has breaking changes.
  / 此 PR 包含破坏性变更。

• This PR changes public API, config, storage format, or migration behavior.
  / 此 PR 修改了公开 API、配置、存储格式或迁移行为。

• This PR requires corresponding changes in related repositories.
  / 此 PR 需要关联仓库同步修改。

Related repository PRs / 关联仓库 PR:

• OpenList-Frontend:
• OpenList-Docs:

Related Issues / 关联 Issue

Fixes #180

Testing / 测试

• go test ./...
• TypeScript check: yarn tsc:check
  / TypeScript 检查：yarn tsc:check
• Static validation: git diff --check and targeted source review.
  / 静态验证：git diff --check 及针对性源码审查。

Checklist / 检查清单

• I have read CONTRIBUTING.
  / 我已阅读 CONTRIBUTING。
• I confirm this contribution follows the repository license, contribution policy, and code of conduct.
  / 我确认此贡献符合仓库许可证、贡献规范和行为准则。
• I have formatted the changed code with gofmt, go fmt, or prettier where applicable.
  / 我已按适用情况使用 gofmt、go fmt 或 prettier 格式化变更代码。
• I have requested review from relevant maintainers or code owners where applicable.
  / 我已在适用情况下请求相关维护者或代码所有者审查。

AI Disclosure / AI 使用声明

• This PR includes AI-assisted content.
  / 此 PR 包含 AI 辅助内容。

Tools used / 使用工具:

• ChatGPT
• Codex
• GitHub Copilot
• Claude
• Gemini
• Other (please specify) / 其他（请注明）:

Usage scope / 使用范围:

• Code generation / 代码生成

• Refactoring / 重构

• Documentation / 文档

• Tests / 测试

• Translation / 翻译

• Review assistance / 审查辅助

• I have reviewed and validated all AI-assisted content included in this PR.
  / 我已审核并验证此 PR 中的所有 AI 辅助内容。

• I have ensured that all AI-assisted commits include Co-Authored-By attribution.
  / 我已确保所有 AI 辅助提交都包含 Co-Authored-By 归属信息。

• I can reproduce all AI-assisted content included in this PR without any AI tools.
  / 我可以在没有任何 AI 工具的情况下重现此 PR 中包含的所有 AI 辅助内容。