chore(security): resolve devDependency audit warnings

[innerdvations]

What does it do?

• Clears pnpm audit for the root workspace without using pnpm.overrides.
• Bumps or replaces dev tooling: ESLint 9.39.4, TypeScript-ESLint 8.59.3, eslint-plugin-import-x (replacing eslint-plugin-import), lint-staged 17, rollup 4.60.4, @rollup/plugin-commonjs 29.0.2, @rollup/plugin-terser 1.0.0, rimraf 6.1.3, runtime qs 6.15.1.
• Adds direct devDependencies where they lift the resolved graph: postcss, vite, picomatch, fast-uri, flatted, ajv (patched versions for nested consumers).
• Removes unused @strapi/eslint-config (not referenced by eslint.config.mjs; it pulled a large legacy dependency tree).
• Updates eslint.config.mjs: import-x rule names, ignore demo/** so the root linter does not traverse demo trees.

Why is it needed?

pnpm audit reported multiple high/moderate issues (e.g. postcss, picomatch, vite, fast-uri, minimatch, rollup, serialize-javascript, flatted, ajv). This branch addresses them by upgrading upstream packages and tightening the ESLint setup, avoiding lockfile-only overrides.

How to test it?

From the repo root with Node in the supported engine range:

pnpm install
pnpm run lint
pnpm test
pnpm run build
pnpm audit

Related issue(s)/PR(s)

N/A