feat(storage-api-client): require BranchAwareClient for swapTables

The /tables/{id}/swap route is only registered under
/v2/storage/branch/{branchId}/... (isAvailableWithoutBranch: false),
so calling swapTables() on a plain Client previously produced a
confusing 404. Mirror the existing guard pattern used by
refreshTableInformationInBucket() and pullTableToBranch() and throw
a ClientException with a clear message instead.

Update the SwapTableTest call sites to use a BranchAwareClient and
add an explicit test for the new guard.

Author: zajca

src/Keboola/StorageApi/Client.php

@@ -1439,6 +1439,10 @@ public function dropTable($tableId, $options = ['async' => true])
      */
     public function swapTables(string $tableId, string $targetTableId): array
     {
+        if (!$this instanceof BranchAwareClient) {
+            throw new ClientException('Swapping tables is supported only in dev branch. Use BranchAwareClient instance.');
+        }
+
         /** @var array<string, mixed> $result */
         $result = $this->apiPostJson("tables/{$tableId}/swap", [
             'targetTableId' => $targetTableId,