📦 添加虚拟环境和启动脚本

新增:
- backend/venv/ - Python 虚拟环境
- backend/start.sh - 启动脚本（使用虚拟环境）
- backend/requirements.txt - 依赖列表
- .gitignore - 忽略虚拟环境和缓存文件

说明:
- 每个项目使用独立虚拟环境
- 避免依赖冲突
- 启动脚本自动创建和激活虚拟环境

frontend/node_modules/@babel/plugin-transform-runtime/src/get-runtime-path/browser.ts

@@ -0,0 +1,15 @@
+export default function (
+  moduleName: string,
+  dirname: string,
+  absoluteRuntime: string | boolean,
+) {
+  if (absoluteRuntime === false) return moduleName;
+
+  resolveFSPath();
+}
+
+export function resolveFSPath() {
+  throw new Error(
+    "The 'absoluteRuntime' option is not supported when using @babel/standalone.",
+  );
+}

frontend/node_modules/@babel/plugin-transform-runtime/src/get-runtime-path/index.ts

@@ -0,0 +1,42 @@
+import path from "node:path";
+
+import { createRequire } from "node:module";
+const require = createRequire(import.meta.url);
+
+export default function (
+  moduleName: string,
+  dirname: string,
+  absoluteRuntime: string | boolean,
+) {
+  if (absoluteRuntime === false) return moduleName;
+
+  return resolveAbsoluteRuntime(
+    moduleName,
+    path.resolve(dirname, absoluteRuntime === true ? "." : absoluteRuntime),
+  );
+}
+
+function resolveAbsoluteRuntime(moduleName: string, dirname: string) {
+  try {
+    return path
+      .dirname(
+        require.resolve(`${moduleName}/package.json`, { paths: [dirname] }),
+      )
+      .replace(/\\/g, "/");
+  } catch (err) {
+    if (err.code !== "MODULE_NOT_FOUND") throw err;
+
+    throw Object.assign(
+      new Error(`Failed to resolve "${moduleName}" relative to "${dirname}"`),
+      {
+        code: "BABEL_RUNTIME_NOT_FOUND",
+        runtime: moduleName,
+        dirname,
+      },
+    );
+  }
+}
+
+export function resolveFSPath(path: string) {
+  return require.resolve(path).replace(/\\/g, "/");
+}