feat: add Astraflow provider support

[ucloudnb666]

Summary

Adds Astraflow (by UCloud / 优刻得) as a supported LLM provider. Astraflow is an OpenAI-compatible AI model aggregation platform supporting 200+ models.

Two variants are registered to cover both endpoints:

Variant	provider_interface key	Endpoint
Astraflow	astraflow	https://api-us-ca.umodelverse.ai/v1 (global)
AstraflowCN	astraflow_cn	https://api.modelverse.cn/v1 (China)

Changes

crates/hermesllm/src/providers/id.rs

• Added Astraflow and AstraflowCN variants to the ProviderId enum
• Added "astraflow" / "astraflow_cn" arms to TryFrom<&str>
• Added explicit _ => return Vec::new() arms in models() (no static model list needed — Astraflow supports 200+ models dynamically configured by the user)
• Added both variants to the OpenAI-compatible arms in compatible_api_for_client() (both AnthropicMessagesAPI and OpenAIChatCompletions translate to OpenAIChatCompletions upstream)
• Added Display arms ("astraflow" / "astraflow_cn")

crates/common/src/configuration.rs

• Added Astraflow and AstraflowCN variants to the LlmProviderType enum (with serde rename attributes)
• Added Display arms for both variants

Usage example

model_providers:
  - name: astraflow/gpt-4o
    provider_interface: astraflow
    access_key: $ASTRAFLOW_API_KEY
    endpoint: api-us-ca.umodelverse.ai
    model: gpt-4o

  - name: astraflow-cn/deepseek-v3
    provider_interface: astraflow_cn
    access_key: $ASTRAFLOW_CN_API_KEY
    endpoint: api.modelverse.cn
    model: deepseek-v3

References

• Global: https://astraflow.ucloud-global.com
• China: https://astraflow.ucloud.cn
• API docs describe full OpenAI-compatible interface (/v1/chat/completions, etc.)