Connections: show each connection's effective node

While checking whether the hosting connections pin an AMI (Task 6637), the answer was only reachable by opening Edit, then Advanced, on each connection, and an empty "Image (AMI id)" box said nothing about what a launch would actually boot. Suggestions: 1. Machines › Connections table: add an "Image" column showing the pinned AMI id, or "Newest Ubuntu 26.04" when blank, so a pin is visible without opening the editor. 2. Edit connection › Advanced › Image (AMI id): when blank, show a placeholder naming the auto behaviour ("Newest Ubuntu 26.04 LTS at each launch"). 3. When a connection pins an AMI, show how old the pin is (the policy re-pins at least every 30 days, docs/policies/information-security.md) and flag it once it is past 30 days. 4. Node detail: show the image id/name the node was launched from, so stale hosts are visible in the console instead of only in EC2. Out of scope: changing how the image is resolved at launch (apps/api/app/cloud_node_launch.py resolve_image). Done means: - The Connections table shows each connection's image (pinned id or the auto label) at desktop and ≤480px widths. - A blank image field shows the auto-behaviour placeholder. - A pin older than 30 days is flagged. - Node detail names the launch image.

Connections now show each image (pinned AMI + age, or Newest Ubuntu 26.04 LTS), flag pins >30d, blank-field placeholder; node/host detail name the launch image. Full gate green bar one flaky test (passes alone); PR #5611 merged, deploy succeeded. Visual check done. Draft follow-up 6686.