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).

backup.sh

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+#
+# ARGUS backup — dumps the database and application data (certificates,
+# uploaded config) into a single, timestamped archive.
+#
+#   cd ~/argus && ./backup.sh [output-directory]
+#
+set -euo pipefail
+
+INSTALL_DIR="${ARGUS_INSTALL_DIR:-$HOME/argus}"
+OUT_DIR="${1:-$PWD}"
+STAMP="$(date +%Y%m%d-%H%M%S)"
+ARCHIVE="${OUT_DIR}/argus-backup-${STAMP}.tar.gz"
+
+bold()  { printf '\033[1m%s\033[0m\n' "$1"; }
+ok()    { printf '  \033[32m✓\033[0m %s\n' "$1"; }
+fail()  { printf '  \033[31m✗\033[0m %s\n' "$1" >&2; exit 1; }
+
+[ -f "$INSTALL_DIR/docker-compose.yml" ] || fail "No ARGUS installation found at $INSTALL_DIR (set ARGUS_INSTALL_DIR if you installed elsewhere)."
+cd "$INSTALL_DIR"
+
+bold "Backing up ARGUS..."
+
+WORKDIR="$(mktemp -d)"
+trap 'rm -rf "$WORKDIR"' EXIT
+
+docker compose exec -T db pg_dump -U "${DB_USER:-postgres}" "${DB_NAME:-argus}" | gzip > "$WORKDIR/db.sql.gz"
+ok "Database dumped"
+
+docker run --rm -v argus_api_data:/data -v "$WORKDIR":/backup alpine \
+  tar czf /backup/api-data.tar.gz -C /data . >/dev/null 2>&1
+ok "Application data archived"
+
+mkdir -p "$OUT_DIR"
+tar czf "$ARCHIVE" -C "$WORKDIR" db.sql.gz api-data.tar.gz
+ok "Backup written to ${ARCHIVE}"
+
+echo
+printf '  %s\n' "Restore with: ./restore.sh ${ARCHIVE}"