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/)

backend/internal/handler/handler.go

@@ -46,6 +46,8 @@ type Handlers struct {
 	Admin          *AdminHandlers
 	Gateway        *GatewayHandler
 	OpenAIGateway  *OpenAIGatewayHandler
+	SoraGateway    *SoraGatewayHandler   // 从本地版本合并
+	SoraClient     *SoraClientHandler    // 从本地版本合并
 	Setting        *SettingHandler
 	Totp           *TotpHandler
 	Payment        *PaymentHandler