Improve: Design specification sheet now shows previews and info

- Always show design sections if preview images exist, even without elements
- Add design preview images to the spec sheet
- Add better error handling for designJson parsing
- Show more useful information even when elements table is empty
- Makes spec sheet more useful for reference and planning

.claude/settings.local.json

@@ -69,7 +69,9 @@
       "Bash(git commit -m 'Fix: Use personalised price in design approval cart add *)",
       "Bash(git commit -m 'Fix: Safely access designJson properties in admin orders page *)",
       "Bash(git commit -m 'Fix: Show personalised price on design review page *)",
-      "Bash(git commit -m 'Fix: Safely parse designJson in admin order detail page *)"
+      "Bash(git commit -m 'Fix: Safely parse designJson in admin order detail page *)",
+      "Bash(xargs grep -l \"design-spec\")",
+      "Bash(git commit -m 'Improve: Design specification sheet now shows previews and info *)"
     ]
   }
 }