chore: justfile + license maintenance

[adamXbot]

Adds a justfile delegating to the repo's real commands (POSIX test harness, the shellcheck.yml lint targets, tag-push release matching release.yml). Extends the existing MIT copyright year from 2022 to 2022-2026 (holder already correct). Opened from the adamXbot fork — the authenticated token has no push access to AdamXweb.

just --list output:

Available recipes:
    default         # List available commands

    [dev]
    lint            # ShellCheck and POSIX syntax check, same targets as CI
    run             # Run the management script's interactive menu
    test            # Run the POSIX test harness (stub docker, no daemon touched)

    [ship]
    release version # Tag and push a release (release.yml attaches manage.sh and its checksum)

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