fix(backup-history): show Total + Other so per-row sums match the count

The "Content Backed Up" panel in Backup History only counted two
categories (Photos + Archives), so a 3-file backup that landed all
3 in business-docs (Ralf's case after the storage truncation +
restore tonight) showed:
  Photos (0 of 0)
  Archives (0)
  → total: 3 files
The discrepancy made admins wonder where the 3 files actually went.

Adds two rows:
  - "Business documents & other" = files_processed - photos - archives
  - "Total files" = files_processed
So the math adds up regardless of which Stage B path the files came
from. Properly per-path-category breakdown requires backend-side
per-path counters (separate follow-up); this commit closes the
visible-discrepancy gap without that schema change.

i18n: en + de added; other locales fall back to en until reviewed.

frontend/src/components/admin/BackupHistory.jsx

@@ -281,7 +281,16 @@ export const BackupHistory = () => {
                                 </div>
                               </div>
 
-                              {/* Content Backed Up */}
+                              {/* Content Backed Up
+                                  Stage B's config-driven walker covers 7 path categories
+                                  (events/active, events/archived, thumbnails, previews,
+                                  heroes, uploads, business-docs). This pane historically
+                                  only counted 2 of them (photos + archives), so the
+                                  per-row sums never matched the total — Ralf 2026-05-30
+                                  flagged a 3 files total with 0+0 visible breakdown.
+                                  Adds an explicit Total + an "Other" bucket so the
+                                  arithmetic adds up even when the backend doesn't yet
+                                  expose per-path counts. */}
                               <div className="space-y-2">
                                 <h4 className="font-medium text-neutral-900 dark:text-neutral-100">{t('backup.history.details.contentBackedUp')}</h4>
                                 <div className="space-y-2">
@@ -301,6 +310,28 @@ export const BackupHistory = () => {
                                       Archives ({stats.archives_backed_up || 0})
                                     </span>
                                   </div>
+                                  {(() => {
+                                    const total = Number(stats.files_processed) || 0;
+                                    const accounted =
+                                      (Number(stats.photos_backed_up) || 0)
+                                      + (Number(stats.archives_backed_up) || 0);
+                                    const other = Math.max(total - accounted, 0);
+                                    return (
+                                      <>
+                                        <div className="flex items-center space-x-2">
+                                          <FileArchive className={`h-4 w-4 ${other > 0 ? 'text-green-500' : 'text-neutral-300 dark:text-neutral-600'}`} />
+                                          <span className="text-sm text-neutral-700 dark:text-neutral-300">
+                                            {t('backup.history.details.otherFiles', 'Business documents & other')} ({other})
+                                          </span>
+                                        </div>
+                                        <div className="flex items-center space-x-2 pt-1 border-t border-neutral-200 dark:border-neutral-700">
+                                          <span className="text-xs uppercase tracking-wide text-neutral-500 dark:text-neutral-400">
+                                            {t('backup.history.details.totalFiles', 'Total files')}: {total}
+                                          </span>
+                                        </div>
+                                      </>
+                                    );
+                                  })()}
                                 </div>
                               </div>
 

frontend/src/i18n/locales/de.json

@@ -475,7 +475,9 @@
         "completed": "Abgeschlossen",
         "contentBackedUp": "Gesicherter Inhalt",
         "errorDetails": "Fehlerdetails",
-        "manifest": "Manifest"
+        "manifest": "Manifest",
+        "otherFiles": "Geschäftsdokumente & sonstige",
+        "totalFiles": "Gesamtdateien"
       },
       "pagination": {
         "showing": "Zeige {{from}}-{{to}} von {{total}} Backups",

frontend/src/i18n/locales/en.json

@@ -2366,7 +2366,9 @@
         "completed": "Completed",
         "contentBackedUp": "Content Backed Up",
         "errorDetails": "Error Details",
-        "manifest": "Manifest"
+        "manifest": "Manifest",
+        "otherFiles": "Business documents & other",
+        "totalFiles": "Total files"
       },
       "pagination": {
         "showing": "Showing {{from}}-{{to}} of {{total}} backups",