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.list-schema.json

@@ -8,38 +8,35 @@
     "showCheckboxes": true,
     "showSorting": true,
     "searchTerm": "",
-    "toolbarButtons": [
-      "create"
-    ],
+    "recordUrl": "acme/demo/widgets/update/:id",
+    "toolbarButtons": ["create", "delete"],
     "columns": [
-      {
-        "key": "name",
-        "label": "Name",
-        "searchable": true,
-        "sortable": true
-      },
-      {
-        "key": "code",
-        "label": "Code",
-        "searchable": true,
-        "sortable": true
-      },
-      {
-        "key": "tags",
-        "label": "Tags",
-        "searchable": false,
-        "sortable": false,
-        "type": "relation",
-        "relation": "tags",
-        "select": "name"
-      }
+      { "key": "name", "label": "Name", "searchable": true, "sortable": true },
+      { "key": "code", "label": "Code", "searchable": true, "sortable": true },
+      { "key": "tags", "label": "Tags", "searchable": false, "sortable": false, "type": "relation", "relation": "tags", "select": "name" },
+      { "key": "created_at", "label": "Created", "searchable": false, "sortable": true, "type": "datetime" },
+      { "key": "active", "label": "Active", "searchable": false, "sortable": false, "type": "switch" }
+    ],
+    "filters": [
+      { "name": "active", "label": "Active", "type": "switch", "column": "active", "trueValue": true, "falseValue": false },
+      { "name": "created", "label": "Created", "type": "daterange", "column": "created_at" },
+      { "name": "maker", "label": "Maker", "type": "scope", "scope": "byMaker", "modelClass": "Acme\\Demo\\Models\\Maker", "nameFrom": "name" }
     ],
-    "filters": [],
     "rowActions": [],
     "bulkActions": [],
-    "recordUrl": "acme/demo/widgets/update/:id"
+    "messages": {
+      "create": { "other": "New widget" },
+      "deleteConfirm": { "one": "Delete :count widget?", "other": "Delete :count widgets?" },
+      "deleteSelected": { "other": "Delete selected" },
+      "deleted": { "one": "Deleted :count widget", "other": "Deleted :count widgets" },
+      "empty": { "other": "No widgets yet." },
+      "emptySearch": { "other": "Nothing found" },
+      "emptySearchHint": { "other": "No widget matches “:term”." },
+      "recordCount": { "one": ":count widget", "other": ":count widgets" },
+      "searchPrompt": { "other": "Search widgets…" },
+      "selected": { "other": "Selected :count" }
+    },
+    "meta": { "locale": "en" }
   },
-  "meta": {
-    "locale": "en"
-  }
+  "meta": { "locale": "en" }
 }