feat: add SMS verification registration with UniSMS provider

- Add phone field to user model with index and helper methods
- Implement SMS provider interface with UniSMS (合一短信) implementation
- Add SMS verification code sending endpoint with rate limiting (1/60s)
- Support SMS registration in Register() (mutually exclusive with email)
- Add SMS configuration to admin settings (provider, keys, signature, template)
- Display phone number in admin user list contact column
- Add i18n translations for all SMS-related messages (zh-CN, en, zh-TW)
- Add Claude Code skills: sync-upstream, migrate-server
- Update CLAUDE.md with git conventions and deployment guide

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

i18n/locales/zh-CN.yaml

@@ -91,6 +91,12 @@ user.wechat_id_empty: "WeChat id 为空！"
 user.telegram_id_empty: "Telegram id 为空！"
 user.telegram_not_bound: "该 Telegram 账户未绑定"
 user.linux_do_id_empty: "Linux DO id 为空！"
+user.sms_verification_required: "管理员开启了短信验证，请输入手机号和验证码"
+user.phone_format_invalid: "手机号格式不正确"
+user.phone_already_taken: "该手机号已被注册"
+user.send_sms_failed: "短信发送失败，请稍后重试"
+user.sms_not_configured: "短信服务未配置"
+user.phone_empty: "手机号不能为空"
 
 # Quota messages
 quota.negative: "额度不能为负数！"