feat: History tab on Upload page with one-click Re-export ZIP

Add a second tab to the Upload page that surfaces the persisted batch
archive and lets the user re-download any 837P batch as a ZIP without
re-parsing the original file.

- Backend: /api/batches now carries per-row claimIds (837P only).
  835 batches return an empty list, which the UI uses as the signal
  to hide the Re-export button on those rows. Avoids an extra
  round-trip to /api/batches/{id} per row.
- Frontend: BatchSummary.claimIds added to the list-endpoint type.
- Upload page: page body wrapped in Tabs.Root with a History trigger
  that mirrors ?tab= in the URL for deep-link round-trip. The
  History tab renders UploadHistory → HistoryTable → HistoryRow with
  a one-click Re-export ZIP button per 837P row. The button calls
  POST /api/batches/{id}/export-837 with the row's claim ids and
  downloads the ZIP via downloadBlob. Falls back to the in-memory
  parsedBatches store when the backend returns no rows so the tab
  stays useful in sample-data mode.
- Backend tests: claimIds present on 837P rows, empty on 835 rows.
- Frontend tests: 13 tests covering tab switching, URL deep-link,
  loading/error/empty states, the 837P-vs-835 button visibility
  split, the Re-export happy path, and the failure toast.

src/lib/api.ts

@@ -171,6 +171,14 @@ export interface BatchSummary {
   inputFilename: string;
   parsedAt: string;
   claimCount: number;
+  /**
+   * Per-claim ids for 837P batches. Empty for 835 (no re-export
+   * endpoint) — the UI hides the one-click Re-export button when
+   * this is empty. Lets the History tab call
+   * `POST /api/batches/{id}/export-837` directly with the row's ids
+   * instead of an extra round-trip to `/api/batches/{id}`.
+   */
+  claimIds: string[];
 }
 
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