feat(17-04): menu:import-winter with the D-05 type map and read-only export SQL

- link to url, blog_categories to all-journal-categories, --map old=new on top; page entries dropped
- entries of unknown types or stale registry references dropped with their subtree, one report line per dropped or remapped entry
- ids, menu_id, parent_id, nest columns and sort_order kept; setval for both tables; --force, --dry-run, empty files copy nothing
- scripts/winter-export-menus.sql and winter-export-entries.sql
- TestMenuImportSmoke

scripts/winter-export-menus.sql

@@ -0,0 +1,25 @@
+-- Menus of a WinterCMS site with the Golem15.Menu plugin, one JSON object
+-- per line: the --menus input of menu:import-winter.
+--
+--   mysql -N -B --raw <database> < winter-export-menus.sql > menus.jsonl
+--
+-- Read-only: it selects from the menus table and changes nothing.
+-- JSON_OBJECT needs MySQL 5.7.8+ or MariaDB 10.2.3+.
+--
+-- Check the table name on the server before running:
+--   SHOW TABLES LIKE '%menu_menus';
+-- This file assumes golem15_menu_menus.
+--
+-- Export the entries with winter-export-entries.sql in the same run: the
+-- entries refer to these ids, and the command keeps both.
+SELECT JSON_OBJECT(
+    'id', m.id,
+    'name', m.name,
+    'code', m.code,
+    'is_active', m.is_active,
+    'css_class', m.css_class,
+    'created_at', m.created_at,
+    'updated_at', m.updated_at
+)
+FROM golem15_menu_menus m
+ORDER BY m.id;