refactor: unify post composition — all assets are artefacts

PostDetail now uses Artefacts exclusively for all 4 asset types:
- Caption copy = Artefact with type='copy', copy_type='caption'
- Body copy = Artefact with type='copy', copy_type='body'
- Design = Artefact with type='design'
- Video = Artefact with type='video'

Removed TranslationDetailPanel from PostDetail entirely.
Same ArtefactDetailPanel, same workflow, same version management
for all asset types. Link picker searches artefacts only.

Server: copy_type added to Artefacts schema, accepted in POST/PATCH.
post-composition.js rewritten to use Artefacts table for all pieces.
Content preview fetched from ArtefactVersionTexts.

Translations entity still exists for the standalone Copy page.

Also: version creation rules, submit-review content validation,
reviewer mandatory for translations, artefact creation simplified.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/post-composition.js

@@ -4,15 +4,12 @@ async function getPostComposition(postId) {
   const post = await nocodb.get('Posts', postId);
   if (!post) return null;
 
-  const translations = await nocodb.list('Translations', {
-    where: `(post_id,eq,${postId})`, limit: 100,
-  });
-  const caption = translations.find(t => t.copy_type === 'caption') || null;
-  const bodyCopy = translations.find(t => t.copy_type === 'body' || !t.copy_type) || null;
-
   const artefacts = await nocodb.list('Artefacts', {
     where: `(post_id,eq,${postId})`, limit: 100,
   });
+
+  const caption = artefacts.find(a => a.type === 'copy' && a.copy_type === 'caption') || null;
+  const bodyCopy = artefacts.find(a => a.type === 'copy' && (a.copy_type === 'body' || !a.copy_type)) || null;
   const design = artefacts.find(a => (a.type || 'design') === 'design') || null;
   const video = artefacts.find(a => a.type === 'video') || null;
 
@@ -28,16 +25,21 @@ async function getPostComposition(postId) {
   const hasPieces = caption || bodyCopy || design || video;
   const piecesReady = hasPieces && waitingOn.length === 0;
 
-  // Get translation texts for languages preview
-  const getTexts = async (translationId) => {
+  // Get texts from ArtefactVersionTexts for copy artefacts (content preview + languages)
+  const getTexts = async (artefactId) => {
     try {
-      const texts = await nocodb.list('TranslationTexts', { where: `(translation_id,eq,${translationId})`, limit: 20 });
-      return texts.map(tt => ({ language: tt.language_code || tt.language, status: tt.status || 'draft' }));
-    } catch { return []; }
+      const versions = await nocodb.list('ArtefactVersions', { where: `(artefact_id,eq,${artefactId})`, sort: '-version_number', limit: 1 });
+      if (versions.length === 0) return { texts: [], contentPreview: '' };
+      const texts = await nocodb.list('ArtefactVersionTexts', { where: `(version_id,eq,${versions[0].Id})`, limit: 20 });
+      const languages = texts.map(tt => ({ language: tt.language_code || tt.language, status: tt.status || 'draft' }));
+      const contentPreview = texts.length > 0 ? (texts[0].content || '').slice(0, 120) : '';
+      return { texts: languages, contentPreview };
+    } catch { return { texts: [], contentPreview: '' }; }
   };
+
   const [captionTexts, bodyTexts] = await Promise.all([
-    caption ? getTexts(caption.Id) : [],
-    bodyCopy ? getTexts(bodyCopy.Id) : [],
+    caption ? getTexts(caption.Id) : { texts: [], contentPreview: '' },
+    bodyCopy ? getTexts(bodyCopy.Id) : { texts: [], contentPreview: '' },
   ]);
 
   // Get first attachment for design/video thumbnail
@@ -75,8 +77,8 @@ async function getPostComposition(postId) {
   ]);
 
   return {
-    caption: caption ? { id: caption.Id, title: caption.title, status: caption.status, language: caption.source_language, content_preview: (caption.source_content || '').slice(0, 120), languages: captionTexts, ...captionApprover } : null,
-    body_copy: bodyCopy ? { id: bodyCopy.Id, title: bodyCopy.title, status: bodyCopy.status, language: bodyCopy.source_language, content_preview: (bodyCopy.source_content || '').slice(0, 120), languages: bodyTexts, ...bodyApprover } : null,
+    caption: caption ? { id: caption.Id, title: caption.title, status: caption.status, content_preview: captionTexts.contentPreview, languages: captionTexts.texts, ...captionApprover } : null,
+    body_copy: bodyCopy ? { id: bodyCopy.Id, title: bodyCopy.title, status: bodyCopy.status, content_preview: bodyTexts.contentPreview, languages: bodyTexts.texts, ...bodyApprover } : null,
     design: design ? { id: design.Id, title: design.title, status: design.status, thumbnail_url: designThumb, current_version: design.current_version, ...designApprover } : null,
     video: video ? { id: video.Id, title: video.title, status: video.status, thumbnail_url: videoThumb, current_version: video.current_version, ...videoApprover } : null,
     platforms,