fix: add offline fallback for dev ID verification and prioritize China-accessible API providers
- When backend is unreachable, allow proceeding with format-only validation (offline mode)
- Reorder API endpoints to prioritize China-accessible providers (DeepSeek, Moonshot, 智谱, 云雾)
- Add 🇨🇳 visual indicators for mainland China accessible platforms
- Add AbortController timeout (10s) for auth requests
- Add .cn-ok CSS class for green-highlighted China-compatible tags
Co-authored-by: qinfendebingshuo <207279273+qinfendebingshuo@users.noreply.github.com>