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>

webui/plugins/podman/ajax/system.php

@@ -0,0 +1,76 @@
+<?php
+/**
+ * ajax/system.php
+ *
+ * Backs the Dashboard panel's summary tiles and the service-status line
+ * shown in the page header — aggregates across several libpod endpoints
+ * into the one shape javascript/dashboard.js needs, so the frontend
+ * doesn't have to make (and wait on) five separate round trips.
+ *
+ * Actions (?action=...):
+ *   summary   GET -> counts, storage usage, engine version, ping status
+ */
+
+declare(strict_types=1);
+
+require __DIR__ . '/../include/bootstrap.php';
+
+$action = $_GET['action'] ?? '';
+
+switch ($action) {
+    case 'summary':
+        podman_json_response(system_summary($client, $podmanConfig));
+        break;
+
+    default:
+        podman_json_error("Unknown action '{$action}'", 400);
+}
+
+/** @return array<string,mixed> */
+function system_summary(PodmanClient $client, PodmanConfig $config): array
+{
+    if (!$client->ping()) {
+        return [
+            'reachable' => false,
+            'socketPath' => $config->socketPath,
+        ];
+    }
+
+    $containers = $client->listContainers(true);
+    $running = 0;
+    foreach ($containers as $c) {
+        if (strtolower((string) ($c['State'] ?? '')) === 'running') {
+            $running++;
+        }
+    }
+
+    $pods = $client->listPods();
+    $images = $client->listImages();
+    $volumes = $client->listVolumes();
+    $networks = $client->listNetworks();
+    $info = $client->info();
+    $df = $client->systemDf();
+
+    $imagesSize = 0;
+    foreach (($df['Images'] ?? []) as $img) {
+        $imagesSize += (int) ($img['Size'] ?? 0);
+    }
+
+    return [
+        'reachable' => true,
+        'socketPath' => $config->socketPath,
+        'podmanVersion' => $info['Version']['Version'] ?? null,
+        'containers' => [
+            'total' => count($containers),
+            'running' => $running,
+        ],
+        'pods' => count($pods),
+        'images' => count($images),
+        'volumes' => count($volumes),
+        'networks' => count($networks),
+        'storage' => [
+            'imagesSizeBytes' => $imagesSize,
+            'imagesSizeFormatted' => podman_format_bytes($imagesSize),
+        ],
+    ];
+}