📦 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-plugin-import/index.d.ts

@@ -0,0 +1,33 @@
+import { ESLint, Linter, Rule } from 'eslint';
+
+declare const plugin: ESLint.Plugin & {
+  meta: {
+    name: string;
+    version: string;
+  };
+  configs: {
+    'recommended': Linter.LegacyConfig;
+    'errors': Linter.LegacyConfig;
+    'warnings': Linter.LegacyConfig;
+    'stage-0': Linter.LegacyConfig;
+    'react': Linter.LegacyConfig;
+    'react-native': Linter.LegacyConfig;
+    'electron': Linter.LegacyConfig;
+    'typescript': Linter.LegacyConfig;
+  };
+  flatConfigs: {
+    'recommended': Linter.FlatConfig;
+    'errors': Linter.FlatConfig;
+    'warnings': Linter.FlatConfig;
+    'stage-0': Linter.FlatConfig;
+    'react': Linter.FlatConfig;
+    'react-native': Linter.FlatConfig;
+    'electron': Linter.FlatConfig;
+    'typescript': Linter.FlatConfig;
+  };
+  rules: {
+    [key: string]: Rule.RuleModule;
+  };
+};
+
+export = plugin;