refactor(webui): relocate backup into features/backup/, app-card to shared/

- features/backup/: backup-schema.js, backup-page.js, backup.css (eager).
- shared/js/backup-app-card.js: cross-feature (used by backup AND the
  app-detail Backups tab), so it goes to shared/, not buried in backup.
- Updated paths: feature scripts array, spa.js handleBackup fallback,
  system-loader apps-manager component (app-card), index.html backup.css href.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Signed-off-by: librelad <librelad@digitalangels.vip>

containers/libreportal/frontend/features/backup/index.js

@@ -14,9 +14,9 @@ LP.features.register({
   routes: ['/backup', '/backup*'],
   // Controllers the feature needs; lazy-loaded on first mount (idempotent).
   scripts: [
-    '/js/components/backup/backup-schema.js',
-    '/js/components/backup/backup-page.js',
-    '/js/components/backup/backup-app-card.js',
+    '/features/backup/backup-schema.js',
+    '/features/backup/backup-page.js',
+    '/shared/js/backup-app-card.js',
   ],
 
   async mount(ctx) {

containers/libreportal/frontend/index.html

@@ -18,7 +18,7 @@
   <link rel="stylesheet" href="/css/style.css">
   <link rel="stylesheet" href="/css/ip-whitelist.css">
   <link rel="stylesheet" href="/features/apps/port-manager.css">
-  <link rel="stylesheet" href="/css/backup.css">
+  <link rel="stylesheet" href="/features/backup/backup.css">
   <link rel="stylesheet" href="/css/ssh.css">
   <link rel="stylesheet" href="/css/admin.css">
   <link rel="stylesheet" href="/features/apps/services.css">

containers/libreportal/frontend/js/spa.js

@@ -358,8 +358,8 @@ class LibrePortalSPAClean {
       // backup-page.js + backup-app-card.js are loaded on first navigation.
       // loadScript is idempotent — subsequent /backup navigations are no-ops.
       await Promise.all([
-        this.loadScript('/js/components/backup/backup-page.js'),
-        this.loadScript('/js/components/backup/backup-app-card.js')
+        this.loadScript('/features/backup/backup-page.js'),
+        this.loadScript('/shared/js/backup-app-card.js')
       ]);
       const html = await this.fetchContent('/html/backup-content.html');
       this.loadContent(html, 'Backups');

containers/libreportal/frontend/js/system/system-loader.js

@@ -206,7 +206,7 @@ class SystemLoader {
       scripts: [
         '/features/apps/port-manager.js',
         '/shared/task/task-manager.js',  // Add TaskManager for backup functionality
-        '/js/components/backup/backup-app-card.js',
+        '/shared/js/backup-app-card.js',
         '/features/apps/services-manager.js',
         '/features/apps/tools-manager.js',
         '/features/apps/routing-manager.js',