feat(invoices): surface monthly/manual accumulator drafts in the Bills list

Manual/monthly-cadence customers accumulate logged hours into one running
draft invoice (is_monthly_draft, migration 128). That draft gets a real
invoice number and stamps the hours ("Billed: R-2026-0026"), but listInvoices
hid is_monthly_draft rows from the main list — so the invoice looked lost even
though it existed on the customer's monthly-queue card. It also carried status
'scheduled' despite never auto-sending on manual cadence, reading misleadingly
as "Scheduled".

- Bills list now opts into drafts via a new `includeDrafts` query param
  (GET /admin/invoices → listInvoices includeMonthlyDrafts). Pickers/sub-lists
  that reuse billsService.list leave it off, so they're unaffected.
- Draft rows render a distinct "Draft" badge instead of "Scheduled"
  (transformInvoice already exposes isMonthlyDraft).
- The hours "Billed: R-…" chip now links straight to its invoice.
- i18n: bills.status.draft (de "Entwurf", en "Draft").

frontend/src/pages/admin/bills/BillsListPage.tsx

@@ -47,6 +47,9 @@ export const BillsListPage: React.FC = () => {
       q: search || undefined,
       status: statusFilter.length ? statusFilter : undefined,
       unpaidOnly,
+      // Surface the running monthly/manual accumulator drafts here (they're
+      // badged "Draft"); they're hidden from pickers/sub-lists by default.
+      includeDrafts: true,
       sort, page, pageSize: 25,
     }),
   });
@@ -186,14 +189,23 @@ export const BillsListPage: React.FC = () => {
                           {formatMoney(Number(inv.totalAmountMinor) / 100, inv.currency)}
                         </td>
                         <td className="px-3 py-2">
-                          <span className={`px-2 py-0.5 rounded text-xs font-medium ${
-                            inv.status === 'paid' ? 'bg-green-100 text-green-800'
-                              : inv.status === 'overdue' ? 'bg-red-100 text-red-800'
-                              : inv.status === 'sent' ? 'bg-blue-100 text-blue-800'
-                              : inv.status === 'cancelled' ? 'bg-neutral-200 text-neutral-600'
-                              : inv.status === 'skipped' ? 'bg-neutral-100 text-neutral-500 italic'
-                              : 'bg-amber-100 text-amber-800'
-                          }`}>{t(`bills.status.${inv.status}`, inv.status)}</span>
+                          {inv.isMonthlyDraft ? (
+                            // Running accumulator draft (manual/monthly). It carries
+                            // status 'scheduled' but never auto-sends on manual cadence,
+                            // so badge it honestly as "Draft" rather than "Scheduled".
+                            <span className="px-2 py-0.5 rounded text-xs font-medium bg-purple-100 text-purple-800 dark:bg-purple-900/40 dark:text-purple-200">
+                              {t('bills.status.draft', 'Draft')}
+                            </span>
+                          ) : (
+                            <span className={`px-2 py-0.5 rounded text-xs font-medium ${
+                              inv.status === 'paid' ? 'bg-green-100 text-green-800'
+                                : inv.status === 'overdue' ? 'bg-red-100 text-red-800'
+                                : inv.status === 'sent' ? 'bg-blue-100 text-blue-800'
+                                : inv.status === 'cancelled' ? 'bg-neutral-200 text-neutral-600'
+                                : inv.status === 'skipped' ? 'bg-neutral-100 text-neutral-500 italic'
+                                : 'bg-amber-100 text-amber-800'
+                            }`}>{t(`bills.status.${inv.status}`, inv.status)}</span>
+                          )}
                         </td>
                       </tr>
                     ))}