Add container image update indicators.

Compare local RepoDigests to remote registry manifest digests, show status in the containers table Updates column, and support force recheck with vault credentials for private registries.

test/visual-structure.test.js

@@ -27,6 +27,8 @@ const REQUIRED_IDS = [
   'registry-store-form',
   'pushImageModal',
   'pull-image-credential',
+  'check-image-updates-btn',
+  'containers-table',
   'deploy-view',
   'tunnels-view',
   'swarm-view',
@@ -56,6 +58,8 @@ const REQUIRED_SNIPPETS = [
   'Always pull the image',
   'Add container',
   'Deploy the container',
+  'Updates',
+  'Check updates',
 ]
 
 test('index.html retains critical view landmarks', (t) => {