feat(distribution): production install/update/backup scripts + public-repo sync (#106)

Builds the customer-facing distribution: a curated distribution/ directory
containing only what an end customer needs (production docker-compose.yml
with no build: sections, install.sh/update.sh/uninstall.sh/healthcheck.sh/
backup.sh/restore.sh, a customer-facing CHANGELOG.md, and README/LICENSE/
NOTICE/THIRD_PARTY_LICENSES) — pushed as the initial content of the new
public alleyviper/argus repo.

install.sh: detects OS, validates Docker/Compose, fetches all deployment
files, generates a secure DB password, creates the required Docker
network, pulls images, starts the stack, waits for health, and rotates
the default admin/admin credentials via the auth API — printing the
generated password once at the end.

update.sh/healthcheck.sh/backup.sh/restore.sh/uninstall.sh formalize what
was previously ad-hoc README snippets into real, safe-by-default scripts
(uninstall.sh keeps data unless --remove-data is explicitly passed and
confirmed; restore.sh requires typed confirmation and documents that it
targets a fresh install, not a live merge).

Added a sync-distribution job to release.yml: after a successful release,
mirrors distribution/ into the public repo and creates a matching
(customer-facing, commit-log-free) release marker there. Needs a one-time
setup step — a fine-grained PAT scoped to alleyviper/argus added as the
ARGUS_PUBLIC_REPO_TOKEN secret — the job cleanly no-ops until that's added.

Not yet done: GHCR package visibility (argus-secure-api/-ui/-nginx) is
still private, which blocks a genuine end-to-end curl-install test from a
clean, unauthenticated environment — deferred at the user's request until
they flip it manually (GitHub does not expose this via API).

LICENSE

@@ -0,0 +1,17 @@
+ARGUS Secure — Proprietary Software License
+Copyright (c) 2025-2026 AI4SEC / lmelo. All rights reserved.
+
+** PLACEHOLDER — NOT A FINAL LICENSE **
+
+This repository contains proprietary, commercial software. A complete commercial license
+agreement has not yet been finalized and this file is a placeholder pending legal review.
+
+Until a final license is adopted, no rights are granted to use, copy, modify, merge, publish,
+distribute, sublicense, or sell copies of this software, in whole or in part, except as
+separately agreed in writing with the copyright holder.
+
+This software incorporates third-party open-source components under their own licenses;
+see THIRD_PARTY_LICENSES and NOTICE for details. Nothing in this placeholder alters the terms
+of those third-party components.
+
+TODO before release: replace this file with final commercial/enterprise license text.