feat: batches with dry run, undo, and CSV import and export

- POST /_seo/api/v1/batch runs changes in one transaction: dry_run
  answers the diff and the conflicts (loops, chains, noindex on a
  published record, canonicals to redirected or noindex addresses) and
  rolls back; a refused change refuses the batch (D-12)
- undo of a change or a whole batch from History and through MCP, with
  the undo_stale, undo_loop and undo_gone refusals (D-13)
- CSV export and import of redirects, rules and records by URL: BOM,
  comma or semicolon, formula cells escaped, a dry-run preview, all or
  nothing with via import; the screen's apply token is HMAC-SHA256 over
  the file and a fingerprint of the data (transfer.stale)
- Import and export singleton with the seo_transfer widget action,
  History record actions undo and undo_batch, navigation entry
- MCP tools undo_change, undo_batch, apply_batch, export_csv, import_csv
- TestBatch, TestUndo, TestCSVTransfer, TestLoopRefused mcp and import

controllers/transfer/config_form.yaml

@@ -0,0 +1,14 @@
+# Import and export singleton (UI-SPEC C13): the footer Save stores the
+# delimiter only.
+name: golem15.seo::lang.transfer.title
+form: ~/plugins/golem15/seo/models/transfer/fields.yaml
+modelClass: Golem15\SEO\Models\Transfer
+defaultRedirect: golem15/seo/transfer
+
+update:
+    redirect: golem15/seo/transfer
+    redirectClose: golem15/seo/redirects
+
+messages:
+    update: golem15.seo::lang.transfer.title
+    saved: backend::lang.messages.form.saved