feat(ai): 实现AI模型调用的积分计费功能

- 后端根据请求体中的n参数计算AI调用次数并扣减用户积分
- 添加readAIRequestCount函数解析multipart/form-data和JSON格式的请求体获取调用次数
- 前端Canvas组件中显示预计消耗的积分数量
- 在助手面板、配置节点面板和提示面板中集成积分成本计算和展示
- 优化模型选择器在云端模式下的模型列表显示逻辑
- 添加CreditSymbol组件用于统一积分图标显示
- 实现requestCreditCost函数计算远程调用的积分消耗
- 更新文档中关于积分扣费和模型配置的相关说明

web/src/components/model-picker.tsx

@@ -20,7 +20,7 @@ type ModelPickerProps = {
 export function ModelPicker({ config, value, onChange, className, fullWidth = false, placeholder = "选择模型", onMissingConfig }: ModelPickerProps) {
     const pickerId = useId();
     const [open, setOpen] = useState(false);
-    const options = useMemo(() => Array.from(new Set([value, ...config.models].filter(Boolean))), [config.models, value]);
+    const options = useMemo(() => Array.from(new Set([...(config.channelMode === "local" ? [value] : []), ...config.models].filter(Boolean))), [config.channelMode, config.models, value]);
     const current = value || "";
 
     useEffect(() => {
@@ -36,7 +36,7 @@ export function ModelPicker({ config, value, onChange, className, fullWidth = fa
             open={open}
             value={current}
             onOpenChange={(nextOpen) => {
-                if (nextOpen && !options.length) {
+                if (nextOpen && !options.length && config.channelMode === "local") {
                     onMissingConfig?.();
                     return;
                 }
@@ -77,7 +77,7 @@ export function ModelPicker({ config, value, onChange, className, fullWidth = fa
                     ))
                 ) : (
                     <SelectItem value="__empty__" disabled>
-                        请先到配置里拉取模型列表
+                        {config.channelMode === "remote" ? "暂无可用模型" : "请先到配置里拉取模型列表"}
                     </SelectItem>
                 )}
             </SelectContent>