fix(tasks): treat app:'system' as a sentinel so the LibrePortal logo renders

`libreportal config update` and `libreportal system update` tasks are
submitted with `task.app === 'system'` (see task-actions.js' configUpdate
+ systemUpdate). renderTaskIcons hit its first branch on any truthy
task.app and built an <img src="/icons/apps/system.svg"…> which 404s
(there is no per-app icon called "system"). The onerror handler then
hid the broken image, so those task rows showed only the 🛠️ type emoji
and no LibrePortal logo — visually inconsistent with sibling system-level
rows like "LibrePortal - Finalize Setup" (which happens to carry
`app: 'libreportal'`, matching a real icon, and renders correctly via
the same branch).

Treat `app: 'system'` as a category sentinel rather than a real slug:
skip the per-app icon path, fall through to the system-task branch that
loads /icons/libreportal.svg directly. That icon is already shipped + the
data shape stays intact ('system' is the meaningful category, not a lie
about the app identity).

Net: "LibrePortal - Apply Configuration" and "LibrePortal - System Update"
now show the LibrePortal logo alongside their type emoji, matching the
Setup / Update / Backup-All rows.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Signed-off-by: librelad <librelad@digitalangels.vip>

containers/libreportal/frontend/js/components/tasks/tasks-manager.js

@@ -1014,11 +1014,15 @@ class TasksManager {
      Keeps the layout consistent across every row regardless of source. */
   renderTaskIcons(task) {
     const typeIcon = `<span class="task-type-icon">${this.getTaskTypeIcon(task).icon}</span>`;
-    if (task.app) {
+    // `app: 'system'` is a category sentinel (config_update, system_update, …),
+    // not a real app slug, so it has no /icons/apps/system.svg — fall through
+    // to the LibrePortal-system branch so those tasks still get a logo.
+    const isSystemSentinel = task.app === 'system';
+    if (task.app && !isSystemSentinel) {
       const appIconPath = this.getAppIconPath(task);
       return `${typeIcon}<img src="${appIconPath}" alt="${task.app}" class="task-app-icon" onerror="this.style.display='none'">`;
     }
-    if (this.isLibrePortalSystemTask(task)) {
+    if (isSystemSentinel || this.isLibrePortalSystemTask(task)) {
       return `${typeIcon}<img src="/icons/libreportal.svg" alt="LibrePortal" class="task-app-icon">`;
     }
     return typeIcon;