chore: Pre-commit hooks

[gcgoncalves]

Add prettier, eslint and unit tests to the pre-commit hook.

[marekdano]

Suggestions (non-blocking)

• The hook is heavy for a pre-commit: format:check + lint (whole
  src+e2e) + full build + full vitest run. That's likely tens of seconds
  to minutes on every commit, which tends to push people toward
  git commit --no-verify. Common pattern: run lint-staged (prettier/eslint on
  staged files only) at pre-commit, and move build + the full test suite to a
  pre-push hook or rely on CI. That keeps commits fast while still gating
  pushes.
• Stale comment in eslint.config.js: it warns about "a
  second, differently-configured prettier.config.js one directory up (repo
  root)." That referred to the old monorepo layout; there's no such file in this
  standalone repo. Now that .prettierrc is added, that comment is misleading
  and could be trimmed. Pre-existing, so optional.

[gcgoncalves]

Great point, @marekdano! I'll update accordingly.