Add a cancel action for queued and running backup runs. Queued runs are
cancelled immediately, while running runs are marked for cancellation and
the worker terminates the active rsync process group.
Make dry-run log paths run-specific and add a defensive default dry-run
timeout so stuck dry-runs do not remain running indefinitely.
Remove rsync exit codes from run overview tables while keeping detailed
diagnostics available on the run detail payload.
Move backup execution out of the management command into a reusable
backup runner service that can execute an existing BackupRun record.
Add queue primitives and a run_pobsync_worker command so manual backup
requests can be recorded as queued SQL state and processed outside the
web request path.
Add a worker Docker service and pobsync worker CLI alias, with tests for
queued run creation, worker execution, manual run typing, and command
mapping.
