Revise README.md with feature and usage details

[TheNorthStarYang]

Update README.md to include detailed descriptions of AhaKey Desktop features, components, and usage instructions in both English and Simplified Chinese.

Pull Request / 合并请求

感谢你为 AhaKey 贡献代码、文档、示例或社区项目。
Thank you for contributing to AhaKey.

你可以使用中文或 English 填写本模板。
You may fill out this template in either Chinese or English.

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0. Language / 填写语言

• 中文
• English

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1. Summary / 修改概述

请用 1-3 句话说明这个 PR 做了什么。
Please briefly describe what this PR changes.

Examples / 示例：

• 修复 Windows BLE 重连失败问题
• 更新 macOS 构建说明
• 增加一个 protocol 示例
• Fix Windows BLE reconnect issue
• Update macOS build guide
• Add a protocol example

Summary / 概述：

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2. Type of change / 修改类型

请选择本次 PR 的类型。
Please select the type of this PR.

• Bug fix / Bug 修复
• Documentation / 文档修改
• New feature / 新功能
• Refactor / 重构
• Build or packaging / 构建或打包
• Protocol example / 协议示例
• Community project or showcase / 社区项目或展示
• Other / 其他

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3. Area / 涉及范围

请选择本次修改涉及的部分。
Please select the area affected by this PR.

• desktop
• protocol
• awesome-ahakey
• firmware
• docs
• macOS
• Windows
• Other / 其他

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4. Why is this needed? / 为什么需要这个修改？

请说明这个修改解决了什么问题，或者带来了什么改进。
Please explain what problem this solves or what improvement it brings.

Examples / 示例：

• 当前安装说明缺少 Swift 版本要求，导致新用户容易构建失败。
• 当前 BLE 重连逻辑在 Windows 下偶尔失败，需要增加重试。
• 当前 README 中缺少社区项目提交说明。
• The current install guide does not mention the required Swift version.
• BLE reconnection sometimes fails on Windows.
• The README does not explain how to submit community projects.

Reason / 原因：

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5. How was it tested? / 如何测试？

请选择并补充说明。
Please select and describe how you tested this change.

• Tested locally / 已在本地测试
• Tested on macOS / 已在 macOS 测试
• Tested on Windows / 已在 Windows 测试
• Documentation-only change / 只修改文档，不需要运行测试
• Not tested yet, maintainer help needed / 暂未测试，需要维护者协助确认

Test environment / 测试环境：

• OS:
• App version:
• Firmware version:
• Device:
• Other:

Test steps and result / 测试步骤和结果：

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6. Screenshots, logs, or demo / 截图、日志或 Demo

如果涉及 UI、安装、连接、设备行为或社区项目，请尽量提供截图、日志或 Demo 链接。
If this PR affects UI, installation, connection, device behavior, or a community project, please provide screenshots, logs, or a demo link if possible.

• Screenshot:
• Logs:
• Demo:
• Related issue or discussion:

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7. Documentation / 文档更新

请选择是否需要更新文档。
Please indicate whether documentation was updated.

• Documentation updated / 已更新相关文档
• No documentation needed / 不需要更新文档
• Not sure / 不确定，需要维护者判断

Notes / 说明：

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8. Safety checklist / 风险确认

请确认以下内容。
Please confirm the following.

• This PR does not include API keys, tokens, private keys, personal config, or sensitive files
  本 PR 不包含 API Key、Token、私钥、个人配置或敏感文件

• This PR does not include installers, build artifacts, or unrelated binary files
  本 PR 不包含安装包、编译产物或无关二进制文件

• This PR does not include unauthorized firmware source, hardware files, or production materials
  本 PR 不包含未授权的固件源码、硬件资料或生产资料

• This PR does not intentionally break the default experience for existing users
  本 PR 不会故意破坏现有用户的默认体验

• If this is a large feature, protocol change, or default behavior change, I have opened an Issue or Discussion first
  如果这是大功能、协议变更或默认行为变化，我已经先开 Issue 或 Discussion 讨论

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9. Additional notes / 其他说明

如果还有其他需要维护者知道的内容，请写在这里。
Add anything else maintainers should know.