fix: clearer Club Log / FCC ULS upload-download diagnostics

Club Log: on a failed batch, log the callsign#id of every QSO in it so a
per-record rejection (e.g. a field value nginx's WAF blocks with a 403) can
actually be located instead of hiding behind "batch FAILED".

FCC ULS: catch the maintenance bounce before following it. data.fcc.gov
redirects to www.fcc.gov/system-maintenance during maintenance windows, and
that page then HTTP/2-stream-errors — which surfaced as a cryptic
INTERNAL_ERROR. Detect the redirect and return "try again later".

app.go

@@ -7846,7 +7846,15 @@ func (a *App) runManualUpload(svc extsvc.Service, ids []int64, cfg extsvc.Extern
 					if err != nil {
 						msg = err.Error()
 					}
+					// Name the QSOs in the failing batch so a per-record rejection
+					// (e.g. a field value nginx's WAF blocks with a 403) can actually
+					// be located — otherwise "batch FAILED" hides which contact it is.
+					who := make([]string, 0, len(batch))
+					for _, it := range batch {
+						who = append(who, fmt.Sprintf("%s#%d", it.call, it.id))
+					}
 					emit(fmt.Sprintf("Club Log: batch of %d FAILED: %s", len(batch), msg))
+					applog.Printf("extsvc: Club Log batch FAILED (%s) — QSOs: %s", msg, strings.Join(who, ", "))
 				}
 			}
 		} else {