feat(quota management): add end-user quota check for shared conversations

fix(default free plan): adjust free plan quota limits

feat(application service): add functionality to reset Agent model parameters to default values

api/app/services/app_service.py

@@ -1452,6 +1452,67 @@ class AppService:
         logger.debug("配置不存在，返回默认模板", extra={"app_id": str(app_id)})
         return self._create_default_agent_config(app_id)
 
+    def reset_agent_config(
+            self,
+            *,
+            app_id: uuid.UUID,
+            workspace_id: Optional[uuid.UUID] = None
+    ) -> AgentConfig:
+        """仅将 Agent 模型参数重置为默认值（不影响其他配置）
+
+        Args:
+            app_id: 应用ID
+            workspace_id: 工作空间ID（用于权限验证）
+
+        Returns:
+            AgentConfig: 重置后的配置对象
+        """
+        logger.info("重置 Agent 模型参数为默认值", extra={"app_id": str(app_id)})
+
+        app = self._get_app_or_404(app_id)
+
+        if app.type != "agent":
+            raise BusinessException("只有 Agent 类型应用支持 Agent 配置", BizCode.APP_TYPE_NOT_SUPPORTED)
+
+        self._validate_app_writable(app, workspace_id)
+
+        stmt = select(AgentConfig).where(AgentConfig.app_id == app_id, AgentConfig.is_active.is_(True)).order_by(
+            AgentConfig.updated_at.desc())
+        agent_cfg: Optional[AgentConfig] = self.db.scalars(stmt).first()
+        now = datetime.datetime.now()
+
+        default_model_parameters = {
+            "temperature": 0.7,
+            "max_tokens": 2000,
+            "top_p": 1.0,
+            "frequency_penalty": 0.0,
+            "presence_penalty": 0.0,
+            "n": 1,
+            "stop": None
+        }
+
+        if agent_cfg:
+            agent_cfg.default_model_config_id = None
+            agent_cfg.model_parameters = default_model_parameters
+            agent_cfg.updated_at = now
+        else:
+            agent_cfg = AgentConfig(
+                id=uuid.uuid4(),
+                app_id=app_id,
+                default_model_config_id=None,
+                model_parameters=default_model_parameters,
+                is_active=True,
+                created_at=now,
+                updated_at=now,
+            )
+            self.db.add(agent_cfg)
+
+        self.db.commit()
+        self.db.refresh(agent_cfg)
+
+        logger.info("Agent 模型参数重置成功", extra={"app_id": str(app_id)})
+        return agent_cfg
+
     def _create_default_agent_config(self, app_id: uuid.UUID) -> AgentConfig:
         """创建默认的 Agent 配置模板（不保存到数据库）