feat(provider): add deepseek-ai protocol support for modelscope.cn

[liugangjian]

Description

Fixes #1103

When configuring modelscope.cn with deepseek models like deepseek-ai/DeepSeek-V3.2, users encountered:

unknown protocol "deepseek-ai" in model "deepseek-ai/DeepSeek-V3.2"

Changes

• Added "deepseek-ai/" prefix support in openrouter protocol detection
• Added dedicated deepseek provider inference for models containing "deepseek", "deepseek/", or "deepseek-ai/"
• Enhanced automatic provider selection to properly route deepseek-ai models to DeepSeek API when configured

Testing

• Verified deepseek-ai/DeepSeek-V3.2 works with modelscope.cn
• Confirmed backward compatibility with existing deepseek/ models
• Tested both direct DeepSeek API and OpenRouter routing scenarios

Type of Change

• Bug fix (non-breaking change which fixes an issue)

AI Code Generation

• 🤖 AI Assisted - Human designed the solution, AI helped implement it

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