feat(apple): add a Free up space action to reclaim leaked storage

Delete all transfers only clears core records, and the blob-store cache is
reclaimed by the core's own timer. Neither touches the app's temporary directory
(leftover picker/staging copies — hundreds of MB on macOS) or the stray .Trash
folders that accumulate in app-owned directories and can't be removed via
Files/Finder. Add a non-destructive Free up space button that empties the temp
directory and removes .Trash folders under the core data dir (and, on iOS, the
fixed Documents receive folder), reporting the bytes reclaimed. Guarded against
running while a transfer is in flight; never touches received files, the core
database, or user-chosen macOS receive folders.

localization/strings.json

@@ -3140,6 +3140,68 @@
         "ru": "Вычисление…"
       }
     },
+    "storage_cleaning": {
+      "context": "Settings > Storage: free-up-space button while cleanup runs.",
+      "translations": {
+        "en": "Cleaning up…",
+        "fr": "Nettoyage…",
+        "es": "Limpiando…",
+        "it": "Pulizia…",
+        "de": "Wird bereinigt…",
+        "pt": "A limpar…",
+        "pl": "Czyszczenie…",
+        "nl": "Opschonen…",
+        "ru": "Очистка…"
+      }
+    },
+    "storage_cleanup_busy": {
+      "context": "Settings > Storage: shown when cleanup is blocked by in-flight transfers.",
+      "translations": {
+        "en": "Finish active transfers before freeing up space",
+        "fr": "Terminez les transferts en cours avant de libérer de l'espace",
+        "es": "Finaliza las transferencias activas antes de liberar espacio",
+        "it": "Completa i trasferimenti attivi prima di liberare spazio",
+        "de": "Beende aktive Übertragungen, bevor du Speicher freigibst",
+        "pt": "Conclui as transferências ativas antes de libertar espaço",
+        "pl": "Zakończ aktywne transfery przed zwolnieniem miejsca",
+        "nl": "Voltooi actieve overdrachten voordat je ruimte vrijmaakt",
+        "ru": "Завершите активные передачи перед освобождением места"
+      }
+    },
+    "storage_cleanup_freed": {
+      "context": "Settings > Storage: cleanup success. {size} = amount freed.",
+      "args": [
+        {
+          "name": "size",
+          "type": "string"
+        }
+      ],
+      "translations": {
+        "en": "Freed {size}",
+        "fr": "{size} libéré",
+        "es": "Se liberó {size}",
+        "it": "Liberati {size}",
+        "de": "{size} freigegeben",
+        "pt": "Libertado {size}",
+        "pl": "Zwolniono {size}",
+        "nl": "{size} vrijgemaakt",
+        "ru": "Освобождено {size}"
+      }
+    },
+    "storage_free_up_space": {
+      "context": "Settings > Storage: button that clears temporary files and stray trash.",
+      "translations": {
+        "en": "Free up space",
+        "fr": "Libérer de l'espace",
+        "es": "Liberar espacio",
+        "it": "Libera spazio",
+        "de": "Speicher freigeben",
+        "pt": "Libertar espaço",
+        "pl": "Zwolnij miejsce",
+        "nl": "Ruimte vrijmaken",
+        "ru": "Освободить место"
+      }
+    },
     "storage_delete_transfers": {
       "context": "Settings > Storage: button to delete all transfer records.",
       "translations": {