Upgrade vue-app test project lint toolchain to ESLint 10

[Copilot]

@babel/eslint-parser@7.x only supports eslint ≤9, causing the ESLint language server to crash under ESLint 10 with a Connection reset on the Java side, breaking all TestVue tests.

Changes

package.json

• Drop @babel/eslint-parser and @babel/core — incompatible with ESLint 10, no longer needed
• eslint: ^9.17.0 → ^10.2.0
• @eslint/js: ^9.17.0 → ^10.0.1
• eslint-plugin-vue: ^10.0.0 → ^10.8.0 (first version with explicit ESLint 10 peer dep)

eslint.config.mjs

• Remove @babel/eslint-parser import and parserOptions.parser usage; espree (ESLint built-in) is sufficient
• flat/vue3-essential → flat/essential — the vue3--prefixed aliases were removed in eslint-plugin-vue@10.x

// Before
import vue from 'eslint-plugin-vue';
import babelParser from '@babel/eslint-parser';
import js from '@eslint/js';

export default [
  js.configs.recommended,
  ...vue.configs['flat/vue3-essential'],
  { languageOptions: { parserOptions: { parser: babelParser } } },
];

// After
import vue from 'eslint-plugin-vue';
import js from '@eslint/js';

export default [
  js.configs.recommended,
  ...vue.configs['flat/essential'],
];

.gitignore — add package-lock.json to prevent accidental commits