feat(17-04): menu plugin admin with registry types, URL checks and tree reorder

- golem15.menu plugin, tables golem15_menu_menus and golem15_menu_menu_entries with the PHP columns plus a nullable url_pattern (D-02)
- MenuEntry BeforeSave ports PHP beforeSave: nest columns 0, menu from the parent, sort_order after the menu's last
- entry type dropdown: url, divider and the signpost registry types; reference depends on type through signpost.ReferenceOptions
- URL scheme allowlist (errors.url_scheme), target _self or _blank, menu and parent cycle checks
- menu filter, toolbar reorder/create/delete and config_reorder.yaml partitioned by menu
- navigation Menus with Menus and Menu entries, permission golem15.menu.manage_menu, en and pl phrasebooks
- TestMenuAdminSmoke

plugin.go

@@ -0,0 +1,49 @@
+// Package menu is the golem15.menu plugin: site menus whose entries are
+// links, dividers and items of the framework's menu item type registry,
+// edited in the admin as a tree per menu. A port of the WinterCMS
+// Golem15.Menu plugin.
+package menu
+
+import (
+	"git.golem15.com/golem15/sm-menu-plugin/models"
+	"git.golem15.com/golem15/sm-menu-plugin/updates"
+	"git.golem15.com/golem15/summercms/modules/backpack"
+	"git.golem15.com/golem15/summercms/modules/pact"
+	"git.golem15.com/golem15/summercms/modules/party"
+	"github.com/go-gormigrate/gormigrate/v2"
+)
+
+var (
+	_ party.Plugin       = (*Plugin)(nil)
+	_ pact.HasMigrations = (*Plugin)(nil)
+	_ pact.HasModels     = (*Plugin)(nil)
+)
+
+// Plugin is the golem15.menu plugin.
+type Plugin struct {
+	app *backpack.App
+}
+
+func (p *Plugin) ID() string { return "golem15.menu" }
+
+// Requires is empty: content types come through the framework's menu item
+// type registry, not from a named plugin.
+func (p *Plugin) Requires() []string { return nil }
+
+func (p *Plugin) Register(app *backpack.App) error {
+	p.app = app
+	return nil
+}
+
+func (p *Plugin) Boot(app *backpack.App) error {
+	p.app = app
+	return nil
+}
+
+func (p *Plugin) Migrations() []*gormigrate.Migration { return updates.All() }
+
+func (p *Plugin) Models() []any { return models.All() }
+
+func init() {
+	party.Register(&Plugin{})
+}