Add WeChat direct channel MVP

[xianyu110]

Summary

• add a WeChat direct-channel MVP to the server with QR login, persisted account state, account monitoring, and text message relay
• add CLI commands for paseo wechat login, paseo wechat status, and the top-level paseo wechat-login alias
• translate the root README to Chinese and document the new WeChat setup and usage flow

Testing

• npm run test:unit --workspace=@getpaseo/server -- src/server/wechat/service.test.ts
• PASEO_LOCAL_SPEECH_AUTO_DOWNLOAD=0 PASEO_DICTATION_ENABLED=0 PASEO_VOICE_MODE_ENABLED=0 npx tsx packages/cli/tests/33-wechat.test.ts

Notes

• verified QR login and live WeChat message relay against the local dev daemon
• the WeChat send payload now includes the upstream-required client_id, message_type, and message_state fields so replies render correctly in WeChat

[faithleysath]

I don't think paseo should add wechat channel because wechat cannot provide a friendly user experience. Moreover, there are already many open-source WeChat channel tools available on the community.