feat(sora): 对齐 Sora OAuth 流程并隔离网关请求路径

- 新增并接通 Sora 专用 OAuth 接口与 ST/RT 换取能力
- 完成前端 Sora 授权、RT/ST 手动导入与账号创建流程
- 强化 Sora token 恢复、转发日志与网关路由隔离行为
- 补充后端服务层与路由层相关测试覆盖

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/internal/service/token_refresh_service.go

@@ -43,10 +43,13 @@ func NewTokenRefreshService(
 		stopCh:           make(chan struct{}),
 	}
 
+	openAIRefresher := NewOpenAITokenRefresher(openaiOAuthService, accountRepo)
+	openAIRefresher.SetSyncLinkedSoraAccounts(cfg.TokenRefresh.SyncLinkedSoraAccounts)
+
 	// 注册平台特定的刷新器
 	s.refreshers = []TokenRefresher{
 		NewClaudeTokenRefresher(oauthService),
-		NewOpenAITokenRefresher(openaiOAuthService, accountRepo),
+		openAIRefresher,
 		NewGeminiTokenRefresher(geminiOAuthService),
 		NewAntigravityTokenRefresher(antigravityOAuthService),
 	}