fix(admin): say what actually ages a stored account copy out

The backups page stated "Retention: 90 days", from a constant whose
comment said it matched a backup-prune job. There is no such job: nothing
deletes a stored copy by age. The weekly copy is replaced in place, one
per account; the copy taken before "Delete all data" is deleted by the
account-deletion purge when the grace window ends; an uploaded copy stays
until its account is erased.

The list now carries preWipeCopyDays (the grace window, 0 when no such
copy is taken) instead of retentionDays, and the page says exactly the
three facts above, in every language.

Also drops a re-export of the JSON import row limit nothing imports.

src/components/admin/__tests__/backups-restore-preview.test.tsx

@@ -49,7 +49,7 @@ vi.mock("@tanstack/react-query", () => ({
             createdAt: "2026-09-01T03:00:00.000Z",
           },
         ],
-        retentionDays: 30,
+        preWipeCopyDays: 14,
         schedule: {
           lastSuccessAt: "2026-09-01T03:00:00.000Z",
           lastSuccessAgeDays: 2,

src/components/admin/__tests__/backups-section-empty.test.tsx

@@ -19,7 +19,7 @@ const healthySchedule = {
 const mocks = vi.hoisted(() => ({
   // Mutable so one file can render both a healthy schedule and a broken one;
   // the query mock reads it on every render.
-  queryData: { rows: [], retentionDays: 30 } as Record<string, unknown>,
+  queryData: { rows: [], preWipeCopyDays: 14 } as Record<string, unknown>,
 }));
 
 /**
@@ -80,7 +80,7 @@ primeLocales("de");
 function render(locale: "en" | "de" = "en") {
   mocks.queryData = {
     rows: [],
-    retentionDays: 30,
+    preWipeCopyDays: 14,
     schedule: healthySchedule,
   };
   return renderToStaticMarkup(
@@ -159,7 +159,7 @@ describe("BackupsSection — empty state", () => {
  */
 describe("BackupsSection — schedule health", () => {
   function withSchedule(schedule: Record<string, unknown>) {
-    mocks.queryData = { rows: [], retentionDays: 30, schedule };
+    mocks.queryData = { rows: [], preWipeCopyDays: 14, schedule };
     return renderToStaticMarkup(
       <I18nProvider initialLocale="en">
         <BackupsSection />
@@ -203,7 +203,7 @@ describe("BackupsSection — schedule health", () => {
   });
 
   it("survives a response that predates the schedule field", () => {
-    mocks.queryData = { rows: [], retentionDays: 30 };
+    mocks.queryData = { rows: [], preWipeCopyDays: 14 };
     expect(() =>
       renderToStaticMarkup(
         <I18nProvider initialLocale="en">

src/components/admin/__tests__/offhost-backups-section.test.tsx

@@ -36,7 +36,7 @@ function render(data: BackupsList["offhost"] | null): string {
         ? null
         : ({
             rows: [],
-            retentionDays: 90,
+            preWipeCopyDays: 14,
             schedule: null,
             offhost: data,
           } as unknown as BackupsList),

src/components/admin/backups-section.tsx

@@ -197,9 +197,11 @@ export function BackupsSection() {
           <BackupRowsCards rows={rows} {...rowActions} />
 
           <p className="text-muted-foreground mt-2 text-xs">
-            {t("admin.section.backups.retentionLabel", {
-              days: data!.retentionDays,
-            })}
+            {data!.preWipeCopyDays > 0
+              ? t("admin.section.backups.retentionNote", {
+                  days: data!.preWipeCopyDays,
+                })
+              : t("admin.section.backups.retentionNoteNoGrace")}
           </p>
         </div>
       )}