feat(project-editor): add sticky save/publish bar with validation summary

Mounts a new ProjectEditorSaveBarComponent in the editor page that shows
draft/published status, unsaved-changes indicator, and validation issues,
wiring the Task 8 facade save()/publish()/dirty/status/validationIssues
signals to an actual UI for the first time.

src/app/i18n/translations.ts

@@ -510,6 +510,11 @@ export interface Translations {
     validationMissingWidget: string;
     validationDuplicateNavLinks: string;
     validationInvalidColors: string;
+    statusDraft: string;
+    statusPublished: string;
+    unsavedChanges: string;
+    save: string;
+    publish: string;
   };
   staticPages: {
     notFound: string;