feat(a11y): add a11y infrastructure — skip-nav, announcer, touch CSS, eslint-jsx-a11y

dashboard/eslint.config.js

@@ -1,11 +1,13 @@
 import js from '@eslint/js'
 import globals from 'globals'
+import jsxA11y from 'eslint-plugin-jsx-a11y'
 import reactHooks from 'eslint-plugin-react-hooks'
 import reactRefresh from 'eslint-plugin-react-refresh'
 import tseslint from 'typescript-eslint'
 
 export default tseslint.config(
   { ignores: ['dist'] },
+  jsxA11y.flatConfigs.recommended,
   {
     extends: [js.configs.recommended, ...tseslint.configs.recommended],
     files: ['**/*.{ts,tsx}'],
@@ -30,6 +32,9 @@ export default tseslint.config(
       // 关闭或降级其他规则
       '@typescript-eslint/no-explicit-any': 'warn',
       '@typescript-eslint/no-unused-vars': 'warn',
+      // jsx-a11y: 降级为 warn 避免阻塞构建，后续 Task 17 逐步修复
+      'jsx-a11y/anchor-ambiguous-text': 'warn',
+      'jsx-a11y/no-autofocus': 'warn',
     },
   },
 )