feat(10-03): search, sort, filter, page and bulk-delete any list

- List state (search, sort, dir, page, per_page, filter[<name>]) lives in
  the URL query through parseListQuery/toListQuery; every change is a
  router replace and clears the selection; search is debounced 300 ms and
  resets the page
- DataTable renders the schema columns with a tri-state page checkbox,
  asc/desc/none sorting with aria-sort, selected rows, a sticky header,
  eight skeleton rows while loading and an empty slot
- CellValue renders text (muted dash when empty, arrays comma-joined),
  datetime as YYYY-MM-DD HH:mm and switch as the Tak/Nie pills
- The heading shows the plural recordCount and the create button;
  delete sits in the toolbar, disabled without a selection, and confirms
  with the plural deleteConfirm in a Reka alert dialog before POSTing
  bulk-delete; a 409 shows a danger toast
- FilterBar renders switch (JSON of the option value), daterange
  (from..to) and scope filters (choices from filters/{scope}/options)
- Pagination shows the range, the per-page select over perPageOptions
  (hidden with one choice) and a pager with ellipsis
- The tracer smoke test skips the new checkbox column; new backend::lang
  list keys; boardwalk/dist rebuilt

admin/tests/fixtures/widgets.options.json

@@ -0,0 +1,9 @@
+{
+  "maker": {
+    "data": [
+      { "value": "1", "label": "Acme Works" },
+      { "value": "2", "label": "Bolt & Co" }
+    ],
+    "meta": { "locale": "en" }
+  }
+}