Add reproducible build system, native Unraid plugin, and WebUI

- versions.env pins podman, conmon, crun, netavark, aardvark-dns, passt,
  and fuse-overlayfs to verified upstream source checksums; SlackBuild
  recipes, scripts/build-packages.sh, checksums.sh, release.sh, and
  update-versions.sh implement the reproducible pipeline; GitHub Actions
  workflows build in a Slackware container and publish releases without
  committing any binaries.

- plugin/podman.plg installs/updates/removes all eight packages (the
  seven components plus the plugin's own unraid-podman scaffolding
  package) via upgradepkg, using the official Unraid array-event hook
  mechanism (event/disks_mounted, event/stopping) instead of editing
  /boot/config/go. rc.podman and the sbin/ helper scripts implement
  storage creation, config seeding/sync, preflight checks, autostart
  with per-container Safe-Mode, and package verify/update/rollback.

- webui/plugins/podman implements the Dashboard, Containers, Pods,
  Images, Volumes, Networks, Logs, Terminal, Compose, and Settings
  panels against the approved mockup (webui/mockups/prototype.html),
  talking to podman system service exclusively via PodmanClient.php
  (libpod REST API over the Unix socket), with two documented
  exceptions: Terminal's one-shot exec model and Compose's use of the
  podman compose CLI, since libpod has no REST equivalent for either.

- docs/ARCHITECTURE.md and docs/ROADMAP.md record the design decisions
  and honest current status (syntax-checked, unit- and
  integration-tested against fake sockets/servers; not yet run against
  a real Unraid/Podman/Slackware system).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

scripts/dev/lint.sh

@@ -0,0 +1,34 @@
+#!/bin/bash
+# =============================================================================
+# scripts/dev/lint.sh
+#
+# Local developer entry point mirroring .github/workflows/lint.yml: runs
+# ShellCheck over shell scripts/SlackBuilds and xmllint over plugin/podman.plg.
+# Requires `shellcheck` and `xmllint` (libxml2) to be installed locally.
+# =============================================================================
+
+set -eu
+
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+cd "$REPO_ROOT"
+
+status=0
+
+if command -v shellcheck > /dev/null 2>&1; then
+  echo "==> ShellCheck"
+  find plugin/rc.d plugin/sbin scripts -type f \
+    \( -name '*.sh' -o -name 'rc.*' -o -name '*.SlackBuild' \) \
+    -print0 \
+  | xargs -0 shellcheck --severity=warning --external-sources || status=1
+else
+  echo "!! shellcheck not installed, skipping (install it to match CI: https://www.shellcheck.net/)" >&2
+fi
+
+if command -v xmllint > /dev/null 2>&1; then
+  echo "==> xmllint (plugin/podman.plg)"
+  xmllint --noout plugin/podman.plg || status=1
+else
+  echo "!! xmllint not installed, skipping (part of libxml2-utils)" >&2
+fi
+
+exit "$status"