📦 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/escalade/sync/index.d.mts

@@ -0,0 +1,9 @@
+export type Callback = (
+	directory: string,
+	files: string[],
+) => string | false | void;
+
+export default function (
+	directory: string,
+	callback: Callback,
+): string | void;

frontend/node_modules/escalade/sync/index.d.ts

@@ -0,0 +1,13 @@
+declare namespace escalade {
+	export type Callback = (
+		directory: string,
+		files: string[],
+	) => string | false | void;
+}
+
+declare function escalade(
+	directory: string,
+	callback: escalade.Callback,
+): string | void;
+
+export = escalade;

frontend/node_modules/escalade/sync/index.js

@@ -0,0 +1,18 @@
+const { dirname, resolve } = require('path');
+const { readdirSync, statSync } = require('fs');
+
+module.exports = function (start, callback) {
+	let dir = resolve('.', start);
+	let tmp, stats = statSync(dir);
+
+	if (!stats.isDirectory()) {
+		dir = dirname(dir);
+	}
+
+	while (true) {
+		tmp = callback(dir, readdirSync(dir));
+		if (tmp) return resolve(dir, tmp);
+		dir = dirname(tmp = dir);
+		if (tmp === dir) break;
+	}
+}

frontend/node_modules/escalade/sync/index.mjs

@@ -0,0 +1,18 @@
+import { dirname, resolve } from 'path';
+import { readdirSync, statSync } from 'fs';
+
+export default function (start, callback) {
+	let dir = resolve('.', start);
+	let tmp, stats = statSync(dir);
+
+	if (!stats.isDirectory()) {
+		dir = dirname(dir);
+	}
+
+	while (true) {
+		tmp = callback(dir, readdirSync(dir));
+		if (tmp) return resolve(dir, tmp);
+		dir = dirname(tmp = dir);
+		if (tmp === dir) break;
+	}
+}