Record and show that an image is already on its newest tag

An image that had been checked and is current looked exactly like one
that was never checked.

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

backend/crates/application/src/tests/image_update_tests.rs

@@ -92,7 +92,8 @@ async fn a_check_records_which_findings_the_candidate_fixes() {
     seed(f.findings.clone(), running, Arc::new(MemCluster::default())).await;
 
     let log = VecLog::default();
-    let update = svc.check(GITEA, &log).await.unwrap().unwrap();
+    let update = svc.check(GITEA, &log).await.unwrap();
+    assert!(!update.up_to_date());
     assert_eq!(update.candidate, "gitea/gitea:1.23.0");
     assert_eq!(update.fixed, vec!["CVE-1", "CVE-2"]);
     assert_eq!(update.fixed_counts.critical, 1);
@@ -111,11 +112,19 @@ async fn a_check_records_which_findings_the_candidate_fixes() {
 }
 
 #[tokio::test]
-async fn nothing_is_recorded_when_the_image_is_current() {
+async fn being_up_to_date_is_recorded_as_a_result_too() {
     let (f, svc) = fixture(FakeScanner::default(), &["1.22.3"]);
     let log = VecLog::default();
-    assert!(svc.check(GITEA, &log).await.unwrap().is_none());
-    assert!(f.updates.0.lock().unwrap().is_empty());
+    let update = svc.check(GITEA, &log).await.unwrap();
+    assert!(update.up_to_date(), "no newer tag exists");
+    assert!(update.candidate.is_empty());
+    assert!(update.fixed.is_empty());
+    // the result is stored, so the view can tell "checked and current" from "never checked"
+    assert_eq!(f.updates.0.lock().unwrap().len(), 1);
+    assert_eq!(
+        svc.stored(GITEA).await.unwrap().unwrap().checked_at,
+        update.checked_at
+    );
     assert!(log
         .0
         .lock()