R-621: the hold panel points at the log the hold kept

A held app's page now says, inside the hold panel, that the app's own log from
before it was stopped was kept, with a Napló link to the logs page that serves
it (0b93e1a). Shown only for an update hold with a non-empty kept log
(Manager.HoldLogKept). New copy through the bundle (hu + en), parity case
app_info_hold_log captured when born.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

controller/internal/stacks/manager.go

@@ -1480,6 +1480,18 @@ func (m *Manager) GetLogs(name string, lines int) (string, error) {
 	return output, nil
 }
 
+// HoldLogKept reports whether the hold kept a non-empty log of this app's own output (R-621) — the
+// app page's hold panel then points at the logs page, which serves that kept log (GetLogs). Read-only;
+// false for an unknown app. Pinned by TestR621_HoldPanelPointsAtTheKeptLog (internal/web).
+func (m *Manager) HoldLogKept(name string) bool {
+	stack, ok := m.GetStack(name)
+	if !ok || stack.ComposePath == "" {
+		return false
+	}
+	_, _, kept := latestHoldLog(filepath.Dir(stack.ComposePath))
+	return kept
+}
+
 // latestHoldLog returns the newest non-empty hold-logs/<ts>/compose-logs.txt under a stack dir. The
 // directory names are UTC timestamps (20060102T150405Z), so the lexical order is the time order.
 func latestHoldLog(dir string) (content, ts string, ok bool) {