style(frontend): Prettier config + one-time repo-wide format pass

Prettier 3 (pinned), printWidth 100, double quotes — chosen to match the existing
hand-formatting and minimise reflow. This commit is ONLY the mechanical format pass
(`prettier --write`) plus the config/ignore/scripts, isolated so it never pollutes a
feature diff. Verified behaviour-neutral: typecheck, eslint (0 errors), and vitest
all green before and after. See .git-blame-ignore-revs — `git blame` skips this sha.

frontend/src/components/DataTable.tsx

@@ -3,13 +3,7 @@ import { useTranslation } from "react-i18next";
 import { sortRows, cycleSort, type SortState } from "../lib/columnSort";
 import Pager, { hasPagerContent } from "./Pager";
 import { PageToolbar } from "./PageShell";
-import {
-  ColumnHead,
-  alignClass,
-  filterRows,
-  type Column,
-  type FilterMap,
-} from "./tableHeader";
+import { ColumnHead, alignClass, filterRows, type Column, type FilterMap } from "./tableHeader";
 
 // A reusable, client-side data table: per-column sort + filter (in the header) + pagination,
 // with its sort/filter/page state optionally persisted to localStorage so a reload (F5) keeps
@@ -95,7 +89,7 @@ export default function DataTable<T>({
   // the table keeps its own, seeded from and saved to persistKey.
   const controlledSort = onSortChange !== undefined;
   const [internalSort, setInternalSort] = useState<SortState>(initial.sort);
-  const sort = controlledSort ? sortProp ?? null : internalSort;
+  const sort = controlledSort ? (sortProp ?? null) : internalSort;
   const [filters, setFilters] = useState<FilterMap>(initial.filters);
   const [page, setPage] = useState(initial.page);
   const [size, setSize] = useState(initial.size ?? pageSize);
@@ -253,7 +247,9 @@ export default function DataTable<T>({
       </div>
 
       {paged.length === 0 && (
-        <div className="text-muted py-8 text-center text-sm">{emptyText ?? t("datatable.empty")}</div>
+        <div className="text-muted py-8 text-center text-sm">
+          {emptyText ?? t("datatable.empty")}
+        </div>
       )}
 
       {controlsPosition === "bottom" && controls}