perf: 性能优化与代码质量改进

- 添加4个数据库索引提升查询性能
- 启用ESLint并配置React支持
- 修复ESLint错误（未使用的导入和状态）
- 简化Toast组件UI样式
- 移除重复文件(server.js.backup)
- 清理.gitignore中的.next目录

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.eslintrc.js

@@ -4,16 +4,39 @@ module.exports = {
     node: true,
     es2021: true,
     jest: true,
+    browser: true,
   },
-  extends: ['eslint:recommended'],
+  extends: [
+    'eslint:recommended',
+    'plugin:react/recommended',
+    'plugin:react-hooks/recommended',
+  ],
   parserOptions: {
     ecmaVersion: 'latest',
     sourceType: 'module',
+    ecmaFeatures: {
+      jsx: true,
+    },
+  },
+  settings: {
+    react: {
+      version: 'detect',
+    },
   },
   rules: {
     'no-console': 'off',
     'no-unused-vars': ['error', { argsIgnorePattern: '^_' }],
     'prefer-const': 'error',
     'no-var': 'error',
+    'react/react-in-jsx-scope': 'off',
+    'react/prop-types': 'off',
   },
+  overrides: [
+    {
+      files: ['**/*.js'],
+      rules: {
+        'react/no-unknown-property': ['error', { ignore: ['class'] }],
+      },
+    },
+  ],
 };