Rework Dashboard, add toasts, container folders/icons/WebUI links, detail tabs

Dashboard:
- Plain-count stat tiles (Running/Stopped/Pods/Images/Volumes/Networks)
  separated from a single "Resource Usage" card (CPU/Memory/Swap/Storage
  meter rows) instead of forcing both into one tile grid, which produced
  awkward spanning-tile/dead-cell layouts.
- Fixed CPU usage never changing (libpod's own cpuUtilization is computed
  once and never resampled) by computing it from /proc/stat deltas instead.
- Fixed memory usage reading far too high by using /proc/meminfo's
  MemAvailable instead of libpod's raw (non-reclaimable-aware) memFree.
- Added an Autostart Queue table reusing podman-autostart.sh's own
  failure-counter files.
- Dashboard and Containers now auto-refresh every ~2s (paused when the
  tab is hidden or a modal is open).

Toasts:
- Real success/warn/error/info toast notifications replacing every
  alert() used for one-way feedback, across every panel.

Container detail modal:
- 5 new tabs: Resources, Logs, Console, Events, Healthcheck.

Containers panel:
- Folders to group containers (name + icon), stored in the plugin's own
  folders.json — a folder's header always shows an icon+name+status chip
  per member, matching Unraid's own Docker page folders. "Move to
  Folder" becomes "Remove from Folder" once a container is already
  grouped.
- Containers can carry an icon URL and a WebUI URL (small button next to
  the name), both stored as container labels and auto-filled from
  templates where applicable.
- Settings: an "Add container" control for the Autostart order table.

Fixes:
- Context menus now measure their own rendered size and flip above the
  anchor when there isn't room below, instead of running off-screen.
- Containers table now uses table-layout:fixed with explicit column
  widths — auto layout was shifting every column (and the header) on
  every folder expand/collapse, and briefly again when a flex wrapper
  was mistakenly placed directly on a <td>.

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

webui/plugins/podman/ajax/folders.php

@@ -0,0 +1,91 @@
+<?php
+/**
+ * ajax/folders.php
+ *
+ * Container folders — a purely cosmetic, plugin-owned organizational
+ * feature for the Containers panel. podman/libpod itself has no concept
+ * of "folders"; this is grouping metadata only (name + icon + which
+ * container names belong to it), similar to Unraid's own Docker page's
+ * folders. Stored as JSON at PodmanConfig::$foldersFile — not a
+ * PodmanClient/libpod concern, see Config.php.
+ *
+ * Actions (?action=...):
+ *   list  GET  -> {"folders": [{"id": "...", "name": "...", "icon": "...", "containers": ["name", ...]}, ...]}
+ *   save  POST {"folders": [...]} -> persists the whole list (same
+ *         whole-list-replace pattern settings.php's autostart_save uses
+ *         — the frontend already holds the full, current structure in
+ *         memory after any add/rename/reassign, so there's no need for
+ *         narrower per-folder mutation endpoints)
+ */
+
+declare(strict_types=1);
+
+require __DIR__ . '/../include/bootstrap.php';
+
+$action = $_GET['action'] ?? '';
+
+switch ($action) {
+    case 'list':
+        podman_json_response(['folders' => folders_read($podmanConfig)]);
+        break;
+
+    case 'save':
+        $body = podman_read_json_body();
+        podman_json_response(['folders' => folders_save($podmanConfig, is_array($body['folders'] ?? null) ? $body['folders'] : [])]);
+        break;
+
+    default:
+        podman_json_error("Unknown action '{$action}'", 400);
+}
+
+/** @return array<int,array<string,mixed>> */
+function folders_read(PodmanConfig $config): array
+{
+    if (!is_readable($config->foldersFile)) {
+        return [];
+    }
+    $decoded = json_decode((string) file_get_contents($config->foldersFile), true);
+    return is_array($decoded) ? $decoded : [];
+}
+
+/**
+ * Re-validates and normalizes before writing — a folder with no name (or
+ * whose name became empty through some client-side bug) is silently
+ * dropped rather than persisted as junk that would then need cleaning up
+ * by hand in the JSON file directly.
+ *
+ * @param array<int,mixed> $folders
+ * @return array<int,array<string,mixed>> the normalized list actually written
+ */
+function folders_save(PodmanConfig $config, array $folders): array
+{
+    $clean = [];
+    foreach ($folders as $f) {
+        if (!is_array($f)) {
+            continue;
+        }
+        $name = trim((string) ($f['name'] ?? ''));
+        if ($name === '') {
+            continue;
+        }
+        $containers = [];
+        foreach (($f['containers'] ?? []) as $n) {
+            $n = trim((string) $n);
+            if ($n !== '') {
+                $containers[] = $n;
+            }
+        }
+        $clean[] = [
+            'id' => (string) ($f['id'] ?? '') !== '' ? (string) $f['id'] : bin2hex(random_bytes(6)),
+            'name' => $name,
+            'icon' => trim((string) ($f['icon'] ?? '')),
+            'containers' => $containers,
+        ];
+    }
+
+    if (file_put_contents($config->foldersFile, json_encode($clean, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES), LOCK_EX) === false) {
+        podman_json_error("Could not write {$config->foldersFile}", 500);
+    }
+
+    return $clean;
+}