fix: 使用转换后的模型名计费

计费时使用 requestBody.model（转换后的实际模型名）而不是原始请求的模型名，
这样定价表只需配置后端实际模型的价格即可。

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/providers/index.ts

@@ -176,7 +176,8 @@ class ProxyEndpoint extends OpenAPIRoute {
         return proxyFetch(c, targetChannelConfig, requestBody,
             async (usage: Usage) => {
                 try {
-                    await TokenUtils.processUsage(c, apiKey, model, targetChannelKey, targetChannelConfig, usage);
+                    // 使用转换后的模型名计费
+                    await TokenUtils.processUsage(c, apiKey, requestBody.model, targetChannelKey, targetChannelConfig, usage);
                 } catch (error) {
                     console.error('Error processing usage:', error);
                 }
@@ -284,7 +285,8 @@ class ResponsesProxyEndpoint extends OpenAPIRoute {
         return proxyFetch(c, targetChannelConfig, requestBody,
             async (usage: Usage) => {
                 try {
-                    await TokenUtils.processUsage(c, apiKey, model, targetChannelKey, targetChannelConfig, usage);
+                    // 使用转换后的模型名计费
+                    await TokenUtils.processUsage(c, apiKey, requestBody.model, targetChannelKey, targetChannelConfig, usage);
                 } catch (error) {
                     console.error('Error processing usage:', error);
                 }