feat(账号): 添加 Sora 账号双表同步与创建

- 新增 sora_accounts 表与 accounts.extra GIN 索引\n- OpenAI OAuth 支持同时创建 Sora 账号并同步配置\n- Token 刷新同步关联 Sora 账号凭证与扩展表\n- 增加 Sora 账号连通性测试与前端开关文案

backend/internal/server/api_contract_test.go

@@ -594,7 +594,7 @@ func newContractDeps(t *testing.T) *contractDeps {
 	settingRepo := newStubSettingRepo()
 	settingService := service.NewSettingService(settingRepo, cfg)
 
-	adminService := service.NewAdminService(userRepo, groupRepo, &accountRepo, proxyRepo, apiKeyRepo, redeemRepo, nil, nil, nil, nil)
+	adminService := service.NewAdminService(userRepo, groupRepo, &accountRepo, nil, proxyRepo, apiKeyRepo, redeemRepo, nil, nil, nil, nil)
 	authHandler := handler.NewAuthHandler(cfg, nil, userService, settingService, nil)
 	apiKeyHandler := handler.NewAPIKeyHandler(apiKeyService)
 	usageHandler := handler.NewUsageHandler(usageService, apiKeyService)