Upgrade low-risk dependencies and reduce vulnerabilities

Upgrade core-js v2→v3, @typescript-eslint/* v5→v8, eslint-plugin-jest v27→v29,
lint-staged v15→v16, react-element-to-jsx-string v14→v15, jsdom v14→v25,
and various @types packages. Add npm overrides to patch transitive vulns
(loader-utils, xml2js, tough-cookie, @octokit/*, trim). Replace fs-extra with
native fs.cpSync, remove unused deps (aws-sdk, stmux, mermaid.cli, ip, intl).
Reduces vulnerabilities from 70 to 11 (0 high, 0 critical).

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

Author: LaurentClaes

babel.config.js

@@ -7,7 +7,7 @@ module.exports = function(api) {
     ['@babel/preset-env', {
       'useBuiltIns': 'usage',
       'modules': false,
-      'corejs': '2',
+      'corejs': '3',
     }],
     ['@babel/preset-react', { runtime: 'classic' }],
     ...(isTest ? [['@babel/preset-typescript', { allExtensions: true, isTSX: true }]] : []),