main: 初始化 Face to API 项目

- 添加前端抽卡台与模型配置界面
- 添加 Express API 服务与多厂商模型调用适配
- 配置本地环境示例、构建脚本和忽略规则

server/tokens.ts

@@ -0,0 +1,32 @@
+export type Usage = {
+  inputTokens: number;
+  outputTokens: number;
+  totalTokens: number;
+  estimated: boolean;
+};
+
+export const estimateTokens = (text: string) => {
+  if (!text.trim()) {
+    return 0;
+  }
+
+  const ascii = text.match(/[\x00-\x7F]/g)?.length ?? 0;
+  const nonAscii = text.length - ascii;
+  return Math.max(1, Math.ceil(ascii / 4 + nonAscii / 1.7));
+};
+
+export const normalizeUsage = (
+  prompt: string,
+  output: string,
+  usage?: Partial<Usage> | null
+): Usage => {
+  const inputTokens = usage?.inputTokens ?? estimateTokens(prompt);
+  const outputTokens = usage?.outputTokens ?? estimateTokens(output);
+
+  return {
+    inputTokens,
+    outputTokens,
+    totalTokens: usage?.totalTokens ?? inputTokens + outputTokens,
+    estimated: usage?.estimated ?? !usage
+  };
+};