fix(backup): make the console restore leave instance settings alone

A disaster-recovery snapshot carries the singleton `app_settings` row —
registration, the MFA requirement, the default locale and timezone, module
availability, the notification and AI configuration, the document size cap and
quota — and the restore wrote it back as a side effect of restoring one
account. An operator putting a single record back on Wednesday reconfigured the
whole host from Monday's file, silently, with nothing on screen saying so.

Rebuilding a host from a snapshot is a real case, so the write stays: it is now
`restoreInstanceSettings: true` on the request and a checkbox beside the typed
gate, off unless the operator ticks it. Restoring an account and reconfiguring
the installation are two decisions, so they are two answers.

The 422 confirmation sentence and the dialog copy drop the instance-wide claim;
the opt-in carries it instead, in all seven catalogues. Integration coverage
runs both arms: without the flag the settings row keeps its own values, with it
the file's values land.

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

@@ -140,12 +140,21 @@ describe("BackupsSection — empty state", () => {
     expect(className).not.toMatch(/\b(?:opacity-\d+|text-\S+\/\d+)\b/);
   });
 
-  it("warns in both catalogs that restore overwrites instance-wide settings", () => {
-    expect(de.admin.section.backups.restoreDescription).toMatch(
+  it("names the instance-wide effect on the opt-in that carries it, in both catalogs", () => {
+    // The restore rewrites the host's own settings only when the operator
+    // ticks the box, so the warning belongs to the box rather than to the
+    // sentence above it — and the box has to say what it turns on.
+    expect(de.admin.section.backups.restoreInstanceSettingsLabel).toMatch(
       /instanzweite Einstellungen/i,
     );
-    expect(en.admin.section.backups.restoreDescription).toMatch(
-      /instance-wide settings/i,
+    expect(de.admin.section.backups.restoreInstanceSettingsHint).toMatch(
+      /Installation/,
+    );
+    expect(en.admin.section.backups.restoreInstanceSettingsLabel).toMatch(
+      /instance settings/i,
+    );
+    expect(en.admin.section.backups.restoreInstanceSettingsHint).toMatch(
+      /installation/i,
     );
   });
 });

src/components/admin/backups-section.tsx

@@ -39,6 +39,7 @@ import { Badge } from "@/components/ui/badge";
 import { QueryErrorRow } from "@/components/ui/query-error-row";
 import { SettingsCardActions } from "@/components/settings/_card-actions";
 import { Button } from "@/components/ui/button";
+import { Checkbox } from "@/components/ui/checkbox";
 import { EmptyState } from "@/components/ui/empty-state";
 import { Input } from "@/components/ui/input";
 import { Label } from "@/components/ui/label";
@@ -124,13 +125,18 @@ function RestoreRowDialog({
 }: {
   row: BackupRow;
   pending: boolean;
-  onConfirm: () => void;
+  onConfirm: (options: { restoreInstanceSettings: boolean }) => void;
 }) {
   const { t } = useTranslations();
   const fmt = useFormatters();
   const [open, setOpen] = useState(false);
   const [typed, setTyped] = useState("");
   const matched = typed.trim() === "RESTORE";
+  // Off unless the operator says otherwise. A disaster-recovery snapshot
+  // carries the host's own settings alongside the account's data, and putting
+  // one account back is not a reason to reconfigure the installation for
+  // everybody on it — so the second effect is a second decision.
+  const [withInstanceSettings, setWithInstanceSettings] = useState(false);
 
   // v1.37.20 — restore preview: fetch what the file contains the moment the
   // dialog opens, so the typed confirmation is an informed one. Derived from
@@ -170,7 +176,10 @@ function RestoreRowDialog({
       open={open}
       onOpenChange={(next) => {
         setOpen(next);
-        if (!next) setTyped("");
+        if (!next) {
+          setTyped("");
+          setWithInstanceSettings(false);
+        }
       }}
     >
       <AlertDialogTrigger asChild>
@@ -255,6 +264,26 @@ function RestoreRowDialog({
             </ul>
           )}
         </div>
+        {/* The second decision, before the typed gate rather than after it:
+            the account's data comes back either way, the host's settings only
+            if this is ticked. */}
+        <label
+          className="flex items-start gap-2 text-sm"
+          data-slot="restore-instance-settings"
+        >
+          <Checkbox
+            data-testid="backup-restore-instance-settings"
+            checked={withInstanceSettings}
+            onCheckedChange={(next) => setWithInstanceSettings(next === true)}
+            className="mt-0.5"
+          />
+          <span>
+            {t("admin.section.backups.restoreInstanceSettingsLabel")}
+            <span className="text-muted-foreground block text-xs">
+              {t("admin.section.backups.restoreInstanceSettingsHint")}
+            </span>
+          </span>
+        </label>
         <div className="space-y-2">
           <Label htmlFor={`restore-prompt-${row.id}`}>
             {t("admin.section.backups.restorePromptLabel")}
@@ -279,7 +308,8 @@ function RestoreRowDialog({
               if (!matched) return;
               setOpen(false);
               setTyped("");
-              onConfirm();
+              onConfirm({ restoreInstanceSettings: withInstanceSettings });
+              setWithInstanceSettings(false);
             }}
           >
             {pending
@@ -781,14 +811,20 @@ export function BackupsSection() {
   // and used inline by `<RestoreRowDialog>` below — keeping the
   // mutation here lets the parent invalidate the list query on success.
   const restore = useMutation({
-    mutationFn: async (row: BackupRow) => {
+    mutationFn: async ({
+      row,
+      restoreInstanceSettings,
+    }: {
+      row: BackupRow;
+      restoreInstanceSettings: boolean;
+    }) => {
       // Idempotency-Key prevents a double-click from re-running the
       // destructive transaction. Include the row id so two different
       // backups can both be restored independently in the same minute.
       const idempotencyKey = `restore-${row.id}-${randomId()}`;
       return apiPost<{ restored: true; skipped?: RestoreSkipSummary }>(
         `/api/admin/backups/${row.id}/restore`,
-        { confirm: "RESTORE" },
+        { confirm: "RESTORE", restoreInstanceSettings },
         { headers: { "Idempotency-Key": idempotencyKey } },
       );
     },
@@ -1079,9 +1115,11 @@ export function BackupsSection() {
                           row={row}
                           pending={
                             restore.isPending &&
-                            restore.variables?.id === row.id
+                            restore.variables?.row.id === row.id
+                          }
+                          onConfirm={(options) =>
+                            restore.mutate({ row, ...options })
                           }
-                          onConfirm={() => restore.mutate(row)}
                         />
                       </div>
                     </td>
@@ -1139,9 +1177,12 @@ export function BackupsSection() {
                     <RestoreRowDialog
                       row={row}
                       pending={
-                        restore.isPending && restore.variables?.id === row.id
+                        restore.isPending &&
+                        restore.variables?.row.id === row.id
+                      }
+                      onConfirm={(options) =>
+                        restore.mutate({ row, ...options })
                       }
-                      onConfirm={() => restore.mutate(row)}
                     />
                   </div>
                 </li>