feat(15-02): add Posts admin with mlmarkdown and FormatHTML

YAML-driven Posts screen stores translatable markdown and regenerates
content_html in the plugin. Publish writes without access_publish are
refused; list and form queries stay on the principal without
access_other_posts.

Co-authored-by: Cursor <cursoragent@cursor.com>

admin_navigation.go

@@ -0,0 +1,39 @@
+package journal
+
+import (
+	"git.golem15.com/golem15/sm-journal-plugin/controllers"
+	"git.golem15.com/golem15/summercms/modules/pact"
+)
+
+// Navigation is the plugin's Winter registerNavigation() entry: the main
+// item journal (order 300) with its side menu. Categories and tags side
+// items are added when those controllers register (Task 2): cabana boot
+// refuses a NavigationItem.Controller that is not an AdminController.
+func (*Plugin) Navigation() []pact.NavigationItem {
+	return []pact.NavigationItem{
+		{
+			Code:        "journal",
+			Label:       "golem15.journal::lang.journal.menu_label",
+			Icon:        "pencil",
+			Permissions: []string{"golem15.journal.*"},
+			Order:       300,
+			Controller:  controllers.PostsControllerID,
+			SideMenu: []pact.NavigationItem{
+				{
+					Code:        "new_post",
+					Label:       "golem15.journal::lang.posts.new_post",
+					Icon:        "plus",
+					Permissions: []string{controllers.PermissionAccessPosts},
+					Controller:  controllers.PostsControllerID,
+				},
+				{
+					Code:        "posts",
+					Label:       "golem15.journal::lang.journal.posts",
+					Icon:        "copy",
+					Permissions: []string{controllers.PermissionAccessPosts},
+					Controller:  controllers.PostsControllerID,
+				},
+			},
+		},
+	}
+}