Remove buttons: confirm + block program removal with active deployments

The Stage 2 editor split dropped the old confirm() — Remove program/service/job
deleted immediately on click. Restored confirmation on all three (FormFooter
window.confirm with a per-type message).

Removing a program that still has services/jobs referencing it would orphan
their program: ref. Now blocked:
- API: DELETE /config/programs/{name} → 409 'Programs with active jobs or
  services cannot be removed. Delete these first: …' (authoritative).
- App: ProgramFields shows the blocked reason instead of a Remove button when
  the program has deployments.
- CLI: castle delete refuses a program with referencing deployments not named
  the same (which would survive the delete dangling).

Verified live: DELETE program lakehouse → 409. api 52 / cli 24 green; build clean.

app/src/components/detail/ServiceFields.tsx

@@ -119,6 +119,7 @@ export function ServiceFields({ service, onSave, onDelete }: Props) {
         onSave={handleSave}
         onDelete={onDelete ? () => onDelete(service.id) : undefined}
         deleteLabel="Remove service"
+        confirmMessage={`Remove service "${service.id}" from castle.yaml? Run a deploy afterward to tear down its unit.`}
       />
     </div>
   )