Share sheet: Hidden and Storage toggles, plus diagnostics for the missing accounts

Two menu chips start at the account's app settings (hidden filter, storage
scope - now published per account), hidden-on asks for the app's unlock, and
external storage is detected via nc:mount-type incl. everything under a
mount. Adds logging for which accounts get published and why one is skipped.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

ios/Runner/Native/NativeServices.swift

@@ -95,6 +95,7 @@ enum NativeServices {
               let accounts = try? JSONDecoder().decode(SharedAccounts.self, from: data)
             else { throw TransferError(message: "Bad accounts payload.") }
             try SharedAccountStore.save(accounts)
+            NSLog("[ShareAccounts] saved %d account(s), active=%@", accounts.accounts.count, accounts.activeId ?? "none")
           }
         case "clearAccount":
           SharedAccountStore.clear()