Closes r177. Critical DR gap - user home directories and ACME
certificates were not being backed up.
Excludes common caches that can be rebuilt:
- .cache, .npm/_cacache, .bun/install/cache
- node_modules, .nix-profile, .nix-defexpr
- Trash
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>