feat: Add Siliconflow API support

[JohnGump]

• Integrate Siliconflow API client
• Add authentication and API endpoints
• Implement basic API operations
• Add unittest for Siliconflow

[JohnGump]

I've already performed unit testing. When testing, please initialize the parameters of the is_llm_configured() function as follows.
def is_llm_configured():
"""Check if LLM is configured by trying to connect to the server"""
try:
client = create_llm_client("siliconflow")
response = query_llm("test", client, provider="siliconflow")
return response is not None
except:
return False