chore(repo): remove devcontainer, renovate config, and drained cache-cleanup workflow

- Delete .devcontainer/ and its CONTRIBUTING section; the Dev Containers
  setup was undocumented elsewhere and no longer maintained
- Delete renovate.json: Renovate has never opened a PR or dashboard issue
  on this repo; Dependabot security updates are what actually run
- Delete ci-cache-cleanup.yml: it drained legacy Next.js build-cache sticky
  disks left by PRs open before #6080 (2026-07-30); Blacksmith evicts sticky
  disks after 7 days idle, so the backlog is gone and the job is a no-op
- Move vitest.scripts.config.ts to scripts/vitest.config.ts with a pinned
  root so the repo root holds no test config; update test:scripts and
  check:script-tests
- Drop the duplicate husky `prepare` in apps/sim; the root prepare installs
  the hooks

Author: waleedlatif1