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/en.ts

@@ -512,6 +512,11 @@ export const en: Translations = {
     validationMissingWidget: 'A homepage section has a widget with no type.',
     validationDuplicateNavLinks: 'Two or more header navigation links are duplicates.',
     validationInvalidColors: 'One or more theme colors are not valid hex colors.',
+    statusDraft: 'Draft',
+    statusPublished: 'Published',
+    unsavedChanges: 'Unsaved changes',
+    save: 'Save',
+    publish: 'Publish',
   },
   staticPages: {
     notFound: 'Page not found',