Link image findings to their workloads and suggest a fixing image update

Container findings now name the workloads that run the image and link
into the Kubernetes view, which highlights them. An update check asks the
registry for newer tags of the same variant, scans the newest one and
records which of the open findings are gone in it. The image row then
shows the candidate tag, how many findings it fixes and how many remain,
marks those CVEs in the expanded list, and offers to roll every workload
over to it. The check runs as a job, nightly for all running images or on
demand for one.

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

backend/crates/domain/src/lib.rs

@@ -5,6 +5,7 @@ pub mod backup;
 pub mod cluster;
 pub mod error;
 pub mod host;
+pub mod image;
 pub mod jobs;
 pub mod ports;
 pub mod settings;