Add Pod lifecycle management, fix nav registration and context-menu bugs

Pods panel could previously only list pods - there was no way to create
one, start/stop/restart it, or attach a container to it from the UI.
Adds a "New Pod" modal (name + port mappings), a per-pod lifecycle menu
(start/stop/restart/remove), and an optional "Pod" field on the Create
Container modal to join an existing pod's network namespace. Backend
verified live against the real podman socket (/pods/create, /pods/{name}/
restart, container "pod" field).

Also fixes three real bugs found via live testing:
- Podman.page used Menu="Podman" instead of Menu="Tasks:<rank>", so the
  plugin never actually appeared in Unraid's top navigation (traced through
  PageBuilder.php/DefaultPageLayout.php/Navigation/Main.php - only pages
  registered under "Tasks" become top-level tabs).
- app.js's shared context-menu component mis-mapped every item positioned
  after a 'separator' entry to the wrong DOM element (an off-by-one against
  menu.children, which includes the separator <div>s) - so "Remove", which
  always sits after a separator, silently did nothing when clicked. Fixed
  by indexing into querySelectorAll('button') instead.
- That same menu was positioned via "position: absolute" math that assumed
  a viewport-relative containing block, but Unraid's own page wrapper
  (webGui/styles/default-base.css's ".content") sets position:relative,
  so the menu rendered far from its anchor button. Switched to
  "position: fixed" with viewport-relative coordinates.

Incidentally, pods add a hidden "infra" container that was leaking into
the plain Containers list with no working lifecycle of its own (always
"running", so its own Remove was permanently disabled) - now filtered out
via libpod's IsInfra flag. And every action-buttons table cell used
"display: flex" directly on the <td>, which browsers can size
inconsistently row to row - moved onto an inner wrapper div instead, and
bumped .podman-btn-icon's touch target size.

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

webui/plugins/podman/javascript/containers.js

@@ -29,7 +29,7 @@
       '<td>' + cpuMem + '</td>' +
       '<td class="mono podman-row-sub">' + P.escapeHtml(c.ports.join(', ') || '&mdash;') + '</td>' +
       '<td class="tnum">' + P.formatDuration(c.uptimeSeconds) + '</td>' +
-      '<td class="podman-actions">' + actionButtons(c) + '</td>' +
+      '<td class="podman-actions"><div class="podman-actions-row">' + actionButtons(c) + '</div></td>' +
       '</tr>';
   }
 
@@ -325,6 +325,9 @@
       '<div class="podman-modal-field"><label>Network</label>' +
       '<select id="cc-network"><option value="bridge">Bridge (default)</option>' +
       '<option value="host">Host</option><option value="none">None</option></select></div>' +
+      '<div class="podman-modal-field"><label>Pod (optional)</label>' +
+      '<select id="cc-pod"><option value="">None</option></select>' +
+      '<div class="hint">Joins the pod\'s shared network namespace instead of the setting above.</div></div>' +
       '<div class="podman-modal-field"><label>Port mappings</label>' +
       '<div class="podman-row-group" id="cc-ports"></div>' +
       '<button type="button" class="podman-btn podman-btn-ghost" data-add="port">+ Add port</button></div>' +
@@ -388,6 +391,16 @@
       });
     }).catch(function () { /* built-in modes still usable */ });
 
+    P.get('pods', 'list').then(function (pods) {
+      const select = backdrop.querySelector('#cc-pod');
+      pods.forEach(function (p) {
+        const opt = document.createElement('option');
+        opt.value = p.name;
+        opt.textContent = p.name;
+        select.appendChild(opt);
+      });
+    }).catch(function () { /* pod selection stays optional */ });
+
     backdrop.querySelector('#cc-image').focus();
 
     backdrop.querySelector('#cc-save-template').addEventListener('change', function (e) {
@@ -440,6 +453,7 @@
         image: image,
         name: backdrop.querySelector('#cc-name').value.trim(),
         networkMode: networkMode,
+        pod: backdrop.querySelector('#cc-pod').value,
         ports: ports,
         volumes: volumes,
         env: env,