Delete 20 orphaned module directories and 3 stray files from
modules/kubernetes/ that are no longer referenced by any stack.
Remove 7 root-level legacy files including the empty tfstate,
27MB terraform zip, commented-out main.tf, and migration notes.
Clean up commented-out dockerhub_secret and oauth-proxy references
in blog, travel_blog, and city-guesser stacks. Remove stale
frigate config.yaml entry from .gitignore. Remove ephemeral
docs/plans/ directory.
