Qwen2API (Python) —— OpenAI/Anthropic 兼容网关（通义千问）
POST /v1/chat/completions /v1/completions /v1/embeddings
POST /v1/messages /v1/messages/count_tokens
GET  /v1/models
GET  /health /status
鉴权: Authorization: Bearer <key> 或 X-Api-Key: <key>