Adds a mirror-it skill that registers a Gitea push mirror via `tea api` against the push_mirrors endpoint, using Gitea's actual remote_address/remote_username/remote_password fields (never embedding credentials in the mirror URL). Credentials can come from the environment or fall back to a repo-root .env file, and all shell snippets are POSIX-compatible so the skill isn't tied to any one shell. Also ignores .env* files repo-wide.