Bundles PR #39 — the per-container 'Update container' button in the
detail sheet. Tap it on a container with an available image update
and the app fires the GraphQL updateContainer(id) mutation, routed
through a new long-running Apollo client (ADR-0016) configured with
10-minute read/write timeouts. The polling client's 15s read timeout
is untouched.

UI shows an 'Updating container...' pill with a spinner during the
multi-minute server-side image pull + recreate. Next snapshot poll
reveals the post-update state (isUpdateAvailable=false, RUNNING).

ViewModel's updatingContainerIds set is cleared in finally, so failed
or cancelled mutations don't leave the UI stuck.