feat: merge sub2apipro features and add Chinese model pricing
## Merged Features from sub2apipro
- Sora video generation integration (OpenAI Sora API)
- Group management enhancements
- Usage log improvements
- Security headers middleware
## Chinese Model Pricing Updates
- GLM-5, GLM-5-Turbo, GLM-5.1, GLM-4.7, GLM-4.5-Air
- Baichuan4, Baichuan4-Turbo, Baichuan4-Air, Baichuan-M3-Plus
- DeepSeek-V3, DeepSeek-V3.2, DeepSeek-R1
- Qwen3-8B (free), Qwen2.5-72B-Instruct
## URL Whitelist Additions
- api.baichuan-ai.com (百川智能)
- api.siliconflow.cn (硅基流动)
- api.z.ai (智谱国际)
- api.groq.com (Groq加速推理)
## Documentation
- Added merge guide (docs/MERGE_GUIDE.md)
- Added quick reference (docs/MERGE_QUICKREF.md)
- Added review reports (docs/reviews/)
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