fix(builder): un-hide and relabel static-page content editor, warn on publish/remove-language

- KNOWN-ISSUES item 11: the WYSIWYG page content editor was buried inside
  a collapsed Advanced <details>, labeled 'Raw HTML (advanced)'. Moved it
  to the top of the Content tab, unwrapped, relabeled 'Page Content' /
  'Содержимое страницы' / 'Эջի բովանդակություն' with a plain-language
  description. Advanced tab keeps genuinely technical fields (id, slug,
  route, custom template).
- Publish (save-bar) and Remove language (languages-section) had no
  confirmation despite being destructive/high-impact — added
  window.confirm guards using the existing builder.confirm* i18n pattern
  (matches resetDraft/resetSection/dirty-guard precedent), all 3 locales.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/i18n/translations.ts

@@ -572,6 +572,8 @@ export interface Translations {
     save: string;
     publish: string;
     confirmLeaveUnsaved: string;
+    confirmPublish: string;
+    confirmRemoveLanguage: string;
     promptLinkUrl: string;
     promptImageUrl: string;
     promptEmbedUrl: string;
@@ -1039,6 +1041,8 @@ export interface Translations {
     groupSharing: string;
     groupAdvanced: string;
     groupAdvancedHtml: string;
+    pageContentLabel: string;
+    pageContentDesc: string;
     seoExplainDesc: string;
     seoTitleHelp: string;
     seoDescriptionHelp: string;