feat: Add VolcEngine and BytePlus (Pay-per-use & Coding Plan) support

[Maaannnn]

feat: Add VolcEngine and BytePlus (Pay-per-use & Coding Plan) support

Description

This PR adds VolcEngine support (Coding Plan) and BytePlus support (both Pay-per-use and Coding Plan) to Nanobot by providing the correct API settings and schemas.

Added Providers & Endpoint Mapping

Provider Name	API Endpoint	Description
volcengine_coding_plan	ark.cn-beijing.volces.com/api/coding/v3	Volcano Engine Coding Plan
byteplus	ark.ap-southeast.bytepluses.com/api/v3	BytePlus Pay-per-use
byteplus_coding_plan	ark.ap-southeast.bytepluses.com/api/coding/v3	BytePlus Coding Plan

Key Changes

1. Schema Expansion: Updated nanobot/config/schema.py to include new providers.
2. Registry Update: Modified nanobot/providers/registry.py to map providers to their correct API gateways.

Checklist

• No breaking changes
• Accurate API endpoint mapping
• Schemas updated
• No redundant code/files

Note for Maintainers

Adjust provider naming or config if needed.