📦 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/eslint-module-utils/ModuleCache.js

@@ -0,0 +1,52 @@
+'use strict';
+
+exports.__esModule = true;
+
+const log = require('debug')('eslint-module-utils:ModuleCache');
+
+/** @type {import('./ModuleCache').ModuleCache} */
+class ModuleCache {
+  /** @param {typeof import('./ModuleCache').ModuleCache.prototype.map} map */
+  constructor(map) {
+    this.map = map || /** @type {{typeof import('./ModuleCache').ModuleCache.prototype.map} */ new Map();
+  }
+
+  /** @type {typeof import('./ModuleCache').ModuleCache.prototype.set} */
+  set(cacheKey, result) {
+    this.map.set(cacheKey, { result, lastSeen: process.hrtime() });
+    log('setting entry for', cacheKey);
+    return result;
+  }
+
+  /** @type {typeof import('./ModuleCache').ModuleCache.prototype.get} */
+  get(cacheKey, settings) {
+    if (this.map.has(cacheKey)) {
+      const f = this.map.get(cacheKey);
+      // check freshness
+      // @ts-expect-error TS can't narrow properly from `has` and `get`
+      if (process.hrtime(f.lastSeen)[0] < settings.lifetime) { return f.result; }
+    } else {
+      log('cache miss for', cacheKey);
+    }
+    // cache miss
+    return undefined;
+  }
+
+  /** @type {typeof import('./ModuleCache').ModuleCache.getSettings} */
+  static getSettings(settings) {
+    /** @type {ReturnType<typeof ModuleCache.getSettings>} */
+    const cacheSettings = Object.assign({
+      lifetime: 30,  // seconds
+    }, settings['import/cache']);
+
+    // parse infinity
+    // @ts-expect-error the lack of type overlap is because we're abusing `cacheSettings` as a temporary object
+    if (cacheSettings.lifetime === '∞' || cacheSettings.lifetime === 'Infinity') {
+      cacheSettings.lifetime = Infinity;
+    }
+
+    return cacheSettings;
+  }
+}
+
+exports.default = ModuleCache;